KANDAHAR, Afghanistan - NATO's new secretary-general said on his first trip to Afghanistan on Wednesday that new rules on Western airstrikes and ground operations have sharply reduced civilian casualties. But he spoke just hours after outraged Afghan villagers said a pre-dawn airstrike had killed three children and a man in a southern village.

An Associated Press reporter and photographer saw residents of Kowuk bring the bodies of three boys and a man to the guesthouse of the Kandahar governor from their village, which is 20 kilometres north of the provincial capital, Kandahar city. The angry villagers shouted "Death to America! Death to infidels!" as they displayed the corpses in the back of a pickup truck.

The U.S. military said it had killed four insurgents on motorcycles in that area and could not confirm any civilian fatalities, although it was investigating.

The issue of civilian casualties at the hands of foreign troops has caused deep resentment among Afghan people. President Hamid Karzai has repeatedly called on foreign troops to halt airstrikes and raids in Afghan villages.

Soon after assuming command of NATO and U.S. forces last month, Gen. Stanley McChrystal ordered troops to limit the use of airstrikes to prevent civilian casualties. He also told troops to avoid clashes that could lead to civilian deaths.

NATO Secretary-General Anders Fogh Rasmussen said in Kabul that since the new orders were issued there has been "a drastic decline in the number of civilian casualties," although he provided no figures.

"It is our clear intention to do everything possible to reduce the number of civilian casualties to an absolute minimum," the former Danish prime minister said at a joint news conference with Karzai.

He did not address the airstrike outside Kandahar.

Abdur Rahim, the father of the boys and uncle of the slain man, told the AP that he heard a pair of helicopters circling over his compound at 1:30 a.m. Wednesday before they fired two missiles that hit his home. His brother and another son were wounded, he said.

"What was the fault of my innocent children? They were not Taliban," Rahim said. "Did they come here to build our country or kill our innocent children?"

A U.S. military spokeswoman said a helicopter had fired on four insurgents carrying jugs on motorcycles through a field away from a populated area of the local district, Arghandab.

"The helicopter engaged the militants with guns and rockets, however the explosions heard by locals were caused by the jugs the insurgents were carrying exploding," said Capt. Elizabeth Mathias. Commanders on the ground were checking into reports of civilian deaths, she said.

In eastern Afghanistan, meanwhile, a roadside bomb killed two tribal elders and four armed guards Wednesday, said Ahmad Zia Abdulzai, the spokesman for Nangarhar province.

The incident happened in the Pachir Agha district of the province as the six were going to a meeting to discuss road security.

Taliban militants regularly use roadside bombs in their attacks against Afghan and foreign troops.