LAY KUNDI, Afghanistan Dozens of civilians were killed during NATO operations in a volatile southern area of Afghanistan this week that also left many Taliban fighters dead, officials and villagers said Thursday. But a preliminary NATO review found only 12 noncombatants had died.

However, if the civilian death toll given by local leaders and residents from Tuesday's fighting is confirmed, it would be the highest from an operation involving Western forces since the U.S.-led invasion in 2001.

As many as 70 militants were killed in heavy fighting in Panjwayi, a district in the former Taliban stronghold of Kandahar province, according to Maj. Luke Knittig, spokesman for NATO's International Security Assistance Force.

But death toll estimates varied widely. Afghan officials estimated up to 60 Taliban fighters and 85 civilians were killed.

In Kandahar city, east of the fighting, hundreds of mourners attended a mass funeral service Thursday for victims of Tuesday's violence.

"Everyone is very angry at the government and the coalition. There was no Taliban," villager Abdul Aye said through tears at the funeral. He said 22 members of his extended family were killed. "These tragedies just keep continuing."

Lawmaker Habibullah Khan said 22 people were buried overnight in a mass grave in Mirwisa Mina, a village about 20 kilometers (10 miles) west of Kandahar.

NATO spokesman Knittig said three separate clashes in the same region west of Kandahar city targeted militants attacking aid deliveries and reconstruction projects. Troops used "precision strikes" against insurgents, he said.

"Very sadly, civilians continue to get caught up in these engagements with tragic results," Knittig said.

NATO said a preliminary assessment found that 12 civilians died, though the alliance said it couldn't determine if they were killed by Taliban or NATO fire.

The Interior Ministry said 40 civilians and 20 Taliban militants were killed, while a Kandahar provincial council member, Bismallah Afghanmal, said up to 85 civilians died. Another government official, who asked not to be named because "it would cause me problems," said at least 60 died.

Afghanmal said Taliban fighters ran into civilian homes, which were then targeted by NATO forces.

"With insurgents who regard the population as a form of human shield for themselves it obviously makes life very difficult for us, but it does not stop us from making every effort to ensure that we minimize any problems," said Mark Laity, a NATO spokesman.

The U.N. Assistance Mission in Afghanistan said it was "very concerned" by the reports.

"The United Nations has always made clear that the safety and welfare of civilians must always come first and any civilian casualties are unacceptable, without exception," a U.N. statement said.

The Afghan Defense Ministry is heading an investigation, NATO said. But Afghanmal said villagers were tired of investigations.

"An investigation has no meaning," he said. "These kinds of things have happened several times, and they only say 'Sorry.' How can you compensate people who have lost their sons and daughters?"

NATO launched a major offensive in the Panjwayi area in September, and the alliance said it killed more than 500 suspected militants during "Operation Medusa," which the top NATO commander in Afghanistan, Lt. Gen. David Richards, called a "significant success."

Richards last month said reconstruction and development efforts would soon begin in the volatile former Taliban heartland. However, there has since been heavy fighting in the region.

"The government and the coalition told the families that there are no Taliban in the area anymore," said Afghanmal. "If there are no Taliban, then why are they bombing the area?"

At the Kandahar funeral, a villager named Taj Mohammad said 10 members of his family died in the fighting.

"The information was wrong," he said. "There were no militants. Innocent people have been killed."

The reports of civilian casualties come less than a week after NATO airstrikes killed nine civilians in the village of Ashogho in the nearby Zhari district of Kandahar province.

President Hamid Karzai has repeatedly condemned civilian casualties, and last week urged NATO to take "maximum caution during military operations to avoid harming civilians."

A spokesman for Karzai declined immediate comment and the Interior Ministry said it couldn't confirm reports of civilian casualties.

Previously, the worst reported incident of civilian deaths from foreign military action in Afghanistan came in July 2002, when a U.S. airstrike in Uruzgan province killed 46 civilians and wounded 117, many of them celebrating at a wedding party.

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