KABUL, Afghanistan — A suicide bomber targeting American troops instead killed six Afghan civilians on yesterday, while American forces acknowledged carrying out a cross-border missile strike that reportedly killed four civilians in Pakistan.

The civilian deaths on both sides of the border came days before a new Pakistani government is due to be sworn in — one that may prove a less pliant ally in the American-led fight against Islamic militants than President Musharraf has been.

Pakistan yesterday sharply protested the cross-border strike, which it said killed four civilians early Wednesday in the tribal area of North Waziristan. An American military spokesman in Afghanistan said the strike, which was carried out with precision-guided munitions, had been aimed at Taliban militants.

The American spokesman, Major Chris Belcher, said Pakistani authorities had been informed of the strike, but only after the fact. The target was a compound about one mile inside Pakistan where senior aides to Siraj Haqqani, a prominent Taliban commander, were believed to be sheltering.

Fighters often slip back and forth across the rugged, unmarked frontier, and Pakistan’s tribal areas have become a haven for militant groups.

The NATO-led coalition in Afghanistan said this week it considers Haqqani the most dangerous Taliban commander in the Afghan war. He is blamed for orchestrating scores of suicide bombings and other attacks, including one last week that killed two NATO soldiers and injured more than a dozen Afghan civilians.

Yesterday’s attack in Kabul, near its international airport, was aimed at a two-vehicle U.S. military convoy. In addition to at least six civilians killed, more than a dozen others were wounded.

Western news agencies reported that the Taliban claimed responsibility.

Afghan President Karzai called the bombing a cowardly attack, one of many he said was meant to harm innocent civilians. However, public anger over such attacks by militants often rebounds against Mr. Karzai’s government and the presence of more than 50,000 foreign troops.

Fighting between insurgents and NATO-led forces has mainly been concentrated in the country’s south and east. Afghan officials said yesterday that at least 41 militants had been killed by American and Afghan forces in clashes a day earlier in the southwestern province of Nimruz.

The American attack yesterday into Pakistan highlighted a highly sensitive issue in the two nations’ relations. Many Pakistanis consider the strikes a violation of national sovereignty, but Mr. Musharraf’s government is thought to have given tacit assent for some missile strikes aimed at senior Taliban and Al Qaeda figures, usually carried out with unmanned aerial drones.