KABUL — A large blast shook a road near the U.S. Embassy and an American military base in Afghanistan's capital Thursday (last night, Hawaii time), killing at least two people.

The blast hit about 12:10 p.m. local time and smoke could be seen rising from the site soon after. An Associated Press reporter saw two bodies on the ground, both burned and later covered with plastic sheets.

It was not immediately clear what caused the explosion. At least six vehicles were burned, including at least one Humvee with an Italian flag painted on the side. Sirens rang through the area as emergency vehicles arrived.

U.S. military spokeswoman Capt. Elizabeth Mathias said they were aware of the blast but did not have more information. Neither NATO forces nor Afghan officials could immediately be reached for comment.

The explosion was the fourth major attack in the capital in five weeks.

In the latest, a car bomb exploded Sept. 8 near the entrance to the military airport in Kabul in an apparent attack on a NATO convoy, killing three civilians. The Taliban claimed responsibility for the blast.