A roadside bomb blast killed four Afghan soldiers and wounded two others Tuesday in the eastern Kunar province, a coalition military spokesperson said.

The explosion in the mountainous Chawkay district, about 135 miles east of the capital, Kabul, took place during a joint Afghan-U.S. patrol, the spokesperson said on condition of anonymity due to being unauthorized to release the information.

The blast killed four Afghan soldiers instantly, while two more were wounded and evacuated to military medical facilities, the spokesperson said. No U.S. forces were wounded.

The bomb was detonated by remote control, said Kunar provincial police chief Abdul Ghafar, who had no further details.

Some 2,500 Afghan and U.S. soldiers are conducting a joint military operation in Kunar province, which borders Pakistan, to rout out Islamic militants linked to the toppled Taliban regime and Al Qaeda.