ZHARI, Afghanistan - Six American soldiers were killed and at least 10 American and Afghan troops wounded Sunday morning when an explosive-laden car smashed into a small combat outpost here in northwestern Kandahar province.

The U.S. military said it detained two men Sunday evening after the suicide attack, though it was unclear whether the men are connected to the attack. They were arrested after being stopped at a check point and testing positive for TNT on their hands. One of the men earlier had raced a motorcycle toward a combat outpost located about a quarter mile down the road from the bombing site. Soldiers guarding the outpost shot at the man, who abandoned his bike and fled in a cab, military officials said.

The massive explosion, one of the deadliest on coalition troops this month, happened a little before 9 a.m. Sunday, collapsing the roof of a small, mud-walled room along the northern side of the outpost that served as the operations center. During the chaotic scene the first few hours after the explosion, the casualty numbers ticked upwards as soldiers previously unaccounted for were found buried deep in the rubble.

Wounded American and Afghan soldiers were medevaced from the outpost, as other nearby soldiers were sent to the scene to help. Another platoon took over command of the outpost, which was reinforced with concrete barriers, military officials said. Two of the American wounded were flown to larger hospitals for further treatment, and the others will return to duty.

The outpost, set up in the last two weeks, is less than one mile away from Sangsar, the farming village where the Taliban founder Mullah Muhammad Omar held the movement’s charter meeting. The small outpost was jointly manned by an American platoon and Afghan National Army soldiers. Most of the compound was not covered, and the soldiers slept outside in tents.

Units in the surrounding area were on high-alert throughout the day as reports came in of more possible suicide bombers. The battalion here conducted a two-week clearing operation in the area just last month. This part of the Zhari district was the last to be cleared in the effort that started in September. U.S. military officials say that while there has been massive improvement in security since then, the insurgency here is still strong.

The Associated Press reported that the Taliban immediately took responsibility for the bombing, saying it was in retaliation for attacks on its fighters in the last few months.

The assault came days ahead of a major White House review of its Afghan strategy following President Barack Obama’s decision last year to send 30,000 American reinforcements in a bid to reverse gains by the Taliban since they were ousted from power in the 2001 U.S.-led invasion.

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