Taliban insurgents tried to overrun a U.S. Marine outpost with a combination of rocket-propelled grenades and homicide bombers in a brazen attack just after sundown on Sunday.

The Marines and Afghan soldiers fended off the assault, shooting the homicide attackers before they had a chance to detonate their weapons.

The attack took place on the second day of a major offensive to wrest control of this town of 75,000 people from the Taliban insurgents who have dominated it for years.

Also on Sunday, the North Atlantic Treaty Organization said that coalition rockets missed their intended target and killed 12 Afghan civilians.

The Marines and Afghan soldiers landed by helicopter on the first day of the offensive and set up camp at the Koru Chareh bazaar, a central commercial district in Marjah. On Sunday, the troops raised the Afghan flag above the bazaar to send the message that the town was gradually reverting to Kabul's control after years of being ruled by the Taliban.

SLIDESHOW: U.S.-Led Attack in Helmand Province

Michael Yon reports from Afghanistan

Around 7 p.m., however, insurgents launched a barrage of rocket-propelled grenades at the entrance to the outpost. Three men then rushed toward the opening, but the Marines killed them by tossing a volley of hand grenades before they were able to set off their explosives, according to Lt. Col. Calvin Worth, commander of the 1st Battalion, 6th Marine Regiment.

"It's obvious the enemy is trying last-ditch efforts," said Lt. Col. Worth, whose 1,500-strong battalion is spearheading the Marjah offensive. His Company B was the target of Sunday's attack.

Lt. Col. Worth was unsure if there were more fighters waiting to assault the Marine position had the suicide bombers succeeded in getting inside. No Marines or Afghan servicemen were reported injured in the attack.

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