Four US marines have been killed by a roadside bomb blast in Afghanistan's Kunar Province.

The soldiers died after an improvised explosive device ripped through their convoy while on patrol, the US military said in a statement.

It was the deadliest attack on US forces in a month. The frequency of such attacks has been growing.

Local governor Assadullah Wafa blamed militants from the former Taleban regime for the attack.

The US soldiers were on patrol, conducting operations to keep a road open.

They are part of a coalition task force engaged in security and construction projects in the poorest region of Afghanistan.

There have been at least 10 roadside bombs this year, compared to 17 in 2005 and five in 2005.

US-led forces have frequently carried out operations in the border region, targeting senior al-Qaeda leaders suspected to be hiding in the area.

PHOTO CAPTION

Afghan security personnel look on as a vehicle belonging to former Afghan president Sibghatullah Mojadidi, which was damaged in a suicide car bomb attack. (AFP)