U.S. forces killed more than 12 insurgents in a clash in southeastern Afghanistan, the military said Thursday, the latest sign that Taliban-led militants are trying to revive their three-year-old insurgency.

The rebels died late Tuesday when U.S. troops fired artillery and scrambled warplanes after a rocket attack on an American base in Khost (search) province, close to the Pakistani border, a military statement said. It said the planes dropped two 500-pound bombs.

"We were able to see the launching point of the rockets and we brought everything we had to bear on it," Maj. J.R. Mendoza (search), a U.S. Army official based in Khost, said in the statement. "More than a dozen insurgents were killed."

The four rockets fired at the base near Khost city caused no damage or injuries, the statement said.

Taliban militants have vowed to step up their campaign against the 17,000-strong U.S. force in Afghanistan, but reports suggest they have suffered heavy casualties, and American commanders insist they are a waning force.

On Monday, U.S. and Afghan forces exchanged fire with suspected Taliban rebels in the mountains of Zabul province, further south. An Afghan official said 17 guerrillas were killed, including several Chechens and Arabs, although the U.S. military has not released any death toll.