KABUL, Aug. 6 (Xinhua) -- Four U.S. soldiers were killed Thursday in a roadside bomb attack in western Afghanistan, NATO forces said.

    The four troops "died after their vehicle struck an improvised explosive device (IED)," NATO said in a statement.

A U.S. Army soldier positioned in front of a bullet damaged truck scans militant positions following an attack on a transport convoy in the Pesh Valley in Afghanistan's Kunar Province August 4, 2009.

NATO didn't release more details of the attack.

    The incident came as new NATO Secretary General Anders Fogh Rasmussen made his first visit to Afghanistan on Wednesday.

    In August at least 15 international troops have been killed in Afghanistan. International troops suffered their bloodiest month in July as 44 U.S soldiers and 31 from other countries were killed.