Civilian casualties not acceptable: Karzai

"We can no longer accept civilian casualties, the way they occur. It's becoming heavy for us," Karzai told reporters after talks with the heads of the Nato- and US-led forces and representatives of the UN, US embassy and EU.

Afghan and UN investigations found that about 50 civilians, including many women and children, were killed in weekend fighting in western Afghanistan, officials said Wednesday.

The US-led coalition has said 136 Taliban fighters were killed in the clashes, that included bombing raids, with militants in the western province of Herat on Friday and Sunday.

A United Nations investigation had so far found that 49 civilians were killed in the fighting in Shindand district, spokesman Adrian Edwards said.

Police found 51 were dead, western Afghanistan spokesman Akramudin Yawar told AFP.

The meeting came as more than 1,000 students in the eastern province of Nangarhar demanded the withdrawal of US troops in a fourth day of angry demonstrations over civilians allegedly killed by coalition troops.

"It is becoming a heavy burden and we are not happy about it," Karzai said.

"I hope the international community will find with us, with our relevant ministries, a mechanism that will bring an end to collateral damage, to damage to civilians," he said.