U.S. Marines have mounted a helicopter assault to seize the Taliban-held town of Dahaneh in southern Afghanistan and are fighting gain control of the area ahead of next week's presidential elections.

The assault began before dawn Wednesday, with Marines entering the town as others battled militants in the surrounding mountains.

Associated Press journalists traveling with the first wave say Marines were met with small arms, mortar and rocket propelled grenade fire. Fighting is still under way hours later, with U.S. Marine Harrier jets streaking over the town and dropping flares in a show of force.

Marines have captured several suspects and seized about 66 pounds (30 kilos) of opium.