DAHANEH, Afghanistan » Helicopter-borne Kaneohe Marines backed by Harrier jets stormed into a strategic Taliban-held town in southern Afghanistan before dawn today, battling to gain control of the area ahead of next week's presidential elections.

Associated Press journalists traveling with the first wave said Marines were met with small arms, mortar and rocket-propelled grenade fire as they flew in helicopters over Taliban lines and dropped into the town. Fighting was still under way hours later, with Marine Harrier jets streaking overhead and dropping flares in a show of force.

Other Marines met heavy resistance as they fought to seize control of the mountains surrounding Dahaneh in the southern province of Helmand. Another convoy of Marines rolled into the town despite roadside bomb attacks and gunfire.

The new offensive, named “;Eastern Resolve 2,”; is designed to break the months-long stalemate in this southern valley where the Taliban are solidly entrenched. By occupying Dahaneh, the Marines hope to isolate insurgents in woods and mountains, away from civilian centers.

“;I think this has the potential to be a watershed,”; said Capt. Zachary Martin, commander of Golf Company, 2nd Battalion, 3rd Marines, who led the assault. The battalion is based at Marine Base Hawaii in Kaneohe.

It was the first time NATO troops had entered Dahaneh, which has been under Taliban control for years. Casualty figures were unavailable due to security restrictions.

U.S., NATO and Afghan troops are working to protect voting sites around the country so Afghans can take part in the country's second-ever direct presidential election. Taliban militants have vowed to disrupt the elections, and attacks are on the rise around Afghanistan.

Marines said they had captured several suspects in today's push and seized about 66 pounds of opium, which the militants use to finance their insurgency. Troops hope to restore control of the town so that residents can vote in the presidential election.

The goal of the offensive is to cut off the Taliban from a major rear base and reclaim the area's main market district. It is hoped this would have a ripple effect through neighboring villages, making civilians more willing to cooperate with NATO forces. The Taliban levy taxes in Dahaneh and maintain checkpoints in the area, which serves as a main trading route through northern parts of Helmand, which produces 60 percent of the world's opium.

“;In the long term it could have tremendous effects for the entire province,”; said Martin, whose company is based in the nearby town of Now Zad.

A combined force of some 500 U.S. and Afghan troops took part in the attack, which included helicopters, snipers and female Marines brought in to deal with Afghan women during the compound-by-compound search conducted by Afghan forces that accompanied the Americans.

Martin said the Marines had devised tactics to minimize civilian casualties in the densely populated area. He said troops would strictly limit the type of weapons they used and would stick to a “;proportional response”; when under fire.

Casualties have mounted as U.S. and NATO troops ramp up military operations following President Barack Obama's decision to send thousands more American forces to Afghanistan to cope with the rising Taliban insurgency.

Last month, U.S. and NATO deaths from roadside and suicide bomb blasts in Afghanistan soared sixfold compared with the same month last year, as militants detonated the highest number of bombs of the eight-year war, according to figures released yesterday.