KABUL, Afghanistan, June 10 — A large springtime offensive by Taliban fighters has turned into the strongest show of force by the insurgents since American forces chased the Taliban from power in late 2001, and Afghan and foreign officials and local villagers blame a lack of United States-led coalition forces on the ground for the resurgence.

American forces are handing over operations in southern Afghanistan to a NATO force of mainly Canadian, British and Dutch troops, and militants have taken advantage of the transition to swarm into rural areas.

Coalition and Afghan forces now clash daily with large groups of Taliban fighters across five provinces of southern Afghanistan. In their boldest push, the Taliban fought battles in a district just less than 20 miles outside the southern city of Kandahar in late May, forcing hundreds of people to abandon their villages for refuge in the city and in other towns as coalition forces resorted to aerial bombardment.

The Taliban are running checkpoints on secondary roads and seizing control of remote district centers for a night or two before melting away again. In the most blatant symbol of their dominance of rural areas, the Taliban have even conducted trials under Islamic law, or Shariah, outside official Afghan courts, and recently carried out at least one public execution.

“The situation is really, in the last four years, the most unstable and insecure I have seen,” said Talatbek Masadykov, who is in charge of the United Nations assistance mission in Kandahar.

But he said accounts of just how bad the security situation was differed, particularly after a surge of fighting just west of Kandahar in recent weeks.

“From different tribal people we are hearing that the Taliban are regrouping,” he said, “and from government officials that security is improving.”

One international security official in Kandahar, who has several years of experience in Afghanistan and asked not to be named because of the nature of his information, said members of American and Canadian Special Forces units had told him that they were “not winning against the Taliban.”

“If the central government does not act and coalition forces do not increase, I think it will be impossible to say what will happen,” he said.

This week, clashes have occurred in Oruzgan, Zabul and Helmand Provinces, with the coalition and Afghan Army forces reporting successful missions in which they killed several dozen Taliban fighters. But Afghans in the Char Chine district of Oruzgan Province said that coalition forces had shelled civilians as they were packing up to leave their nearby village, Pir Jawati.

Eleven people were killed, including an old woman and four children, said Mirwais, a shopkeeper in Char Chine who goes by one name and was contacted by telephone. Two suicide bombs this week in Kandahar and Khost killed at least four civilians and a roadside bomb killed three men in a government convoy south of Kabul, the capital, on Saturday.

Officials in the American-led coalition say the Taliban suffered a severe blow when American warplanes bombed the village of Tolokan, not far from Kandahar, on May 21, as part of a four-pronged operation by Afghan and coalition forces over several days.

The bombing killed at least 35 civilians, and immediately afterward much anger was directed at the 25,000 American forces still in Afghanistan, prompting President Hamid Karzai to visit the site.

But local residents say the public mood quickly shifted against the Taliban, as the Tolokan bombing drove home the risk to villagers who, whether because of coercion or cooperation, allow the insurgents into their homes. It also underscored the heavy civilian toll the fighting was taking.

Many Afghans said they simply wanted one side, any side, to bring security.

Southern Afghanistan is the birthplace of the Taliban movement and has remained a stronghold as the Taliban have staged a steady comeback since their fall from power in December 2001.

For several years, they could only field a few hundred men in scattered groups in mountainous areas. Now the Taliban claims to have 12,000 fighters, while coalition estimates add up to perhaps half of that.

Even though several hundred insurgents may have been killed in fighting this year, the Taliban are recruiting ever greater numbers of local people, the officials said.

Many Afghans interviewed expressed frustration that the American-led coalition, which showed such strength in 2001, was now failing to stem the resurgent Taliban and that as a consequence people were dying.

Col. Ian Hope, the Canadian commander of coalition forces in Kandahar Province, acknowledged that his forces had been spread too thin over the past two months to stem the sudden surge in Taliban fighters. But he said that should change with the addition of more Afghan forces and now that British and Dutch forces were getting into place. “It will not occur again,” he said. “It’s dangerous for people to lose confidence in us.”

NATO has deployed a 9,700-member force in Afghanistan that will grow to 16,000, with 6,000 deployed in southern Afghanistan, one of the most restive regions. While NATO is deploying troops, the United States will reduce its force by about 3,000 and keep 20,000 in the country under a separate American chain of command. The American forces will keep responsibility for the volatile eastern region that abuts some of the most lawless areas in Pakistan.

Even though the Tolokan bombing may have hurt the insurgents, local residents say, the Taliban presence remains strong, and villagers dread the prospect of more violence. They complain they are caught in the middle of fighting that pits the Taliban against the government and their foreign allies.

Hajji Agha Lalai, a tribal elder and provincial councilor from the Panjwai district in Kandahar Province, gathered elders in his house several weeks ago to discuss what to do about the intensifying conflict. At a meeting that was held a day after the Tolokan bombing, he said, the death toll finally drove home a consensus: the Taliban must go.

“Everyone swore that we would cooperate with each other and not let the Taliban fight in our district,” he said. “We are not going to pick up guns and fight the Taliban; we are going to go with bare hands, and come out of our houses and tell them: ‘You have to kill us first before you can attack the government and the coalition from here.’ ”

A month ago, 200 to 300 Taliban were moving freely in the Panjwai district and the adjoining district, Zhare, the governor of Kandahar Province, Asadullah Khaled, said in an interview.

After the Tolokan bombing, the coalition forces and government estimated that the Taliban lost up to 80 men in new fighting and reported that the insurgents had pulled out of the district. “The situation in Panjwai has completely changed,” Mr. Khaled said.

Colonel Hope, who took part in the operation in Panjwai, said that the presence of the Taliban was much reduced.

“We believe there are a number of small groups, numbering 10 or 5 men, who want to stay and will change their tactics to I.E.D. attacks,” he said, referring to improvised explosive devices like roadside bombs. “For this reason we need to maintain our presence and security in these districts.”

Yet others, foreign and Afghan officials, were far more pessimistic in their assessments and said urgent and strong action from the coalition and government forces was needed to stem the Taliban advance.

The United Nations agencies in Kandahar reduced their international staff to 25 from 36 because of the security situation, and those staff members not withdrawn from the area were gathering at night in two central guesthouses for safety, said Mr. Masadykov, the head of the assistance mission.

The government lost control of the Chora district in Oruzgan Province to the Taliban for several days at the end of May, until American and Afghan forces mounted an airborne assault to take it back.

In neighboring Helmand Province travelers have reported that the Taliban are running a series of checkpoints north of the main highway up to the towns of Sangin and Kajaki.

At least 200 families have fled their homes in the Panjwai district and taken refuge with relatives in the district center, while more have come to Kandahar, said a tribal elder, Muhammad Alam Agha.

A former mujahadeen commander and landowner in Panjwai, who asked not to be named for fear of reprisals from the Taliban, said, “We told the government for months that the situation was bad, that the Taliban were coming and killing people and that it would get difficult if they became too numerous.”

He and many other villagers abandoned their farms and brought their families to Kandahar. “The Taliban could get into the city, if the government is still sleeping,” he said. He added that he had seen members of the Taliban walking around in Kandahar. “I don’t think the government can turn it around now,” he said.

The Canadian commander of forces in southern Afghanistan, Brig. Gen. David Fraser, is firmly optimistic. “The Taliban have this great ability to blend into the villages and towns,” he said in an interview at his headquarters at the Kandahar air base. “But they are not the superstars people make them out to be. They are capable fighters but defeatable.”

Yet Afghans reported that security had become so bad that people said they did not care which side won, as long as someone took control and ended the fighting.

“We are going mad now,” said Lala Jan, 19, a farmer from Deh Rawud in Oruzgan Province, one of the most strife-torn areas and a Taliban stronghold. “From one side we have the government and Americans, and on the other side the Taliban. When the Taliban come in, they enter without asking, and it’s the same with the Americans. We cannot tolerate any of them.”

Even more evident is the growing public dissatisfaction with the government, especially with the rampant corruption and venality of local officials, which has played into the hands of the Taliban, who are remembered for running a relatively corruption-free government.

Some people have turned to the Taliban to settle local disputes, in particular in parts of Helmand where they dominate, said the director of the Afghan Independent Human Rights Commission in Kandahar, Abdul Qadar Noorzai.

The United Nations special rapporteur for independence of the judiciary, Leandro Despouy, condemned the public execution of a man accused of a crime, Badshah Khan, after a trial by a Taliban court in the remote mountainous province of Daikundi last month.

There is often no government presence in such remote areas, and the Taliban seem to be influencing those tribal leaders who usually decide local matters. “It is entirely unacceptable for a nonstate entity, such as the Taliban, to exercise a state function by trying and punishing an alleged criminal,” Mr. Despouy said in a statement. “The return to the practice of making a public spectacle of the execution harks back to the worst excesses of the old regime.”