KABUL, Afghanistan — Foreign and Afghan forces accidentally killed five children in two separate operations yesterday, further undermining President Karzai after he demanded a halt to attacks in civilian areas.

Afghan officials have accused forces from America and other countries of killing dozens of civilians in recent weeks. The deaths have inflamed tensions across the country and weakened public support for both Mr. Karzai’s government and a continued foreign troop presence in Afghanistan.

NATO said it accidentally killed three children in an artillery strike in the east yesterday after insurgents attacked its troops in the area.

One artillery round slammed into a house in the Gayan district of Paktika province.

A NATO statement said it “deeply regrets this accident, and an investigation as to the exact circumstances of this tragic event is now under way.”

Afghan government officials were not immediately available for comment on yesterday, a national holiday.

In a separate raid, police officer Qubaidullah, who like many Afghans goes by one name, said American troops backed by Afghan intelligence agents killed a man and his two children near the capital, Kabul.

However, an American coalition spokesman, 1st Lieutenant Nathan Perry, said no American troops took part in the operation. NATO said it could not confirm its troops had participated.

Angry men gathered at the victims’ house in the Utkheil area east of Kabul where the three bodies were displayed inside a mud-walled compound, a relative, Yahya Khan, said.

American and NATO officials say they do all they can to minimize civilian deaths and accuse militants of hiding and firing at them from civilian homes.

But Mr. Karzai called on American and NATO commanders last month to stop their airstrikes in civilian areas of Afghanistan, and instead go after terror centers in neighboring Pakistan. The Taliban and other insurgents use the deaths as leverage to turn Afghans away from the government, he says.

In another sign that the civilian deaths are undermining NATO’s mission, the alliance issued an unusual statement Sunday warning that the Taliban planned to make a false claim about the killings of civilians in the southern Helmand province.