Chapman was the scene of a major attack in December, when a suicide bomber entered the base and killed seven CIA employees.

Maj. Wazir Pacha of the provincial police headquarters said insurgents used rifles, heavy machine guns, rocket propelled grenades, and other heavy weapons, but had been repelled.

"The area is under control, but we still need to find those hiding," he said.

Small arms fire could still be heard in the area midmorning, while NATO helicopters patrolled overhead, according to Associated Press Television.

Police captured a pickup truck laden with ammunition and a light truck packed with explosives that had become stuck in deep mud, Pacha said, adding that police suspected the light truck was an intended suicide truck bomb.

Zabihullah Mujahid, a spokesman for the Taliban, said 30 fighters had attacked one of the base. They included suicide bombers and others armed with rockets and machine guns, Mujahid told Reuters by telephone from an undisclosed location.

Despite the presence of almost 150,000 foreign troops, violence across Afghanistan is at its worst since the Taliban were ousted by U.S.-backed Afghan forces in late 2001.

Taliban-led insurgents have launched increasingly brazen attacks around Afghanistan in a bid to topple the government and force out foreign troops. More than 2,000 foreign troops have been killed, most of them Americans, since the conflict began.

Hundreds of civilians have also been caught in the crossfire, with civilian deaths spiking by 31 percent in the first six months of this year, according to a United Nations report.

Contractors killed

Separately, NATO said one of its patrols mistakenly fired on a vehicle carrying private security contractors in Wardak province west of Kabul, killing two men.

It said the patrol had come under Taliban fire early Saturday, then spotted a vehicle approaching fast from behind with a man shooting out its window.

"It is believed that the private security contractors were returning fire against the same insurgents who had just previously attacked the coalition vehicle, and had increased their speed to break contact," the coalition said in a statement.

The incident was under investigation, it said.

Coalition forces and private security contractors frequently come under small arms fire along the stretch of road known as Highway 2 that runs west through perilous country toward the city of Herat.

On Friday, homemade bombs killed three U.S. troops in southern and eastern Afghanistan, bringing the total of foreign troops killed in Afghanistan this month to 55, including 35 Americans, according to a count by The Associated Press. July was the deadliest month for U.S. forces in Afghanistan since the 2001 invasion, with 66 killed.

Poor security is one of the main concerns for Afghans before parliamentary elections on Sept. 18, a milestone after fraud-marred presidential polls last year and with U.S.

President Barack Obama planning a strategy review in December.