The assault, which came as thousands of American troops were taking part in an anti-Taliban offensive hundreds of miles away in the south of Afghanistan, pointed up the insurgents' ability to take the fight to a location of their choosing - in this case a remote outpost in Paktika province, which borders Pakistan's tribal areas.

The incident also illustrated militant groups' continuing capability to stage sophisticated, multipronged attacks in Afghanistan's eastern border zone, despite the Pakistani army's efforts in recent weeks to rein in insurgents who use the tribal areas in Pakistan as a staging ground.

Yesterday's attack on a small base in Zerok district, which lasted several hours, took place in the same area where a U.S. soldier disappeared Tuesday. The U.S. military said two days later that the missing man was believed to have been captured. A search is under way.

American military officials said that "several" U.S. soldiers were wounded in addition to the two killed in the base attack, but declined to provide a more precise figure. Military officials said that at least 10 insurgents were killed in counterstrikes by U.S. and Afghan troops, including artillery fire and attacks by assault helicopters. A spokesman for the governor of Paktika province, however, put the number of militants killed at more than 30.

The attackers fired at least one shell containing white phosphorus, a highly incendiary agent, NATO's International Security Assistance Force said in a statement. Western military officials have accused insurgents of using white phosphorus in several previous attacks.

Hadmidullah Zawak, a spokesman for the provincial governor, said the attackers struck the installation from two sides with rockets, mortars, and small-arms fire and attempted in the midst of the assault to ram an explosives-laden truck through the gates of the base. It detonated, apparently prematurely, after being fired on.

A spokesman for the Taliban movement, Zabiullah Mujaheed, claimed responsibility for the attack, and said more than 100 insurgents took part in it. His statement could not be verified independently. The number of American and Afghan troops inside the base at the time was not disclosed, but the installation is a relatively small one.

With warmer temperatures and the advent of the traditional summer "fighting season," violence across the country has been creeping upward. Afghanistan's Interior Ministry said seven policemen were killed by a roadside bomb in Kandahar province, in the south, and two Afghan army soldiers died in a roadside blast in Helmand province, also in the south.

Helmand is the scene of a major offensive by U.S. Marines, who aim to establish for the first time a large Western troop presence in the lower Helmand River valley, an insurgent stronghold and a center of the opium trade. The Marines so far have met with little significant resistance; military officials have said the Taliban slipped away rather than engaging the attacking force of more than 4,000 Americans and about 600 Afghan troops.