Blast kills 6 guards of U.S. firm

KABUL, Afghanistan (CNN) - A roadside bomb Monday killed six Afghan guards who were accompanying a vehicle of a U.S.-based private security firm, the defense ministry said.

The guards, working for the Texas firm U.S. Protection and Investigations (USPI), were struck Sunday near the town of Gereshk in the Helmand province in southern Afghanistan, said Gen. Mohammad Zahir Azimi.

No one claimed immediate responsibility for the attack. But Azimi said it bore the hallmarks of the hardline militant group, the Taliban.

USPI is based in Houston, Texas, according to the company's Web site. Last December, Taliban fighters ambushed a USPI-operated convoy carrying fuel bound for U.S. military bases in western Afghanistan. Fifteen Afghan employees of the firm were killed in the attack.

Meanwhile, Afghan authorities released further details of the Sunday insurgent attack at an outpost in eastern Afghanistan. The attack, which killed nine American soldiers and wounded 15 others, was the deadliest attack on U.S. troops in Afghanistan in three years.

Azimi said the attack in Dara-I-Pech, in the far eastern province of Kunar, involved 400 to 500 militants. At least 100 were killed or injured, he said.

The casualties also included four Afghan National Army soldiers.