During a lull in a firefight with taliban militants, Afghan Army local commander Mohammed Hussein, left, stands with Marine squad leader Sgt. Matthew Duquette, of Warrenville, Ill., who shouts out orders to Marines from 3rd Platoon, Bravo Company, 1st Battalion 5th Marines, on Sunday in Nawa district, Helmand province, southern Afghanistan.

Kabul ? Hundreds of insurgents armed with automatic rifles and rocket-propelled grenades stormed a pair of remote outposts near the Pakistan border, killing eight U.S. soldiers and capturing more than 20 Afghan security troops in the deadliest assault against U.S. forces in more than a year, military officials said.

The fierce gunbattle, which erupted at dawn Saturday in the Kamdesh district of mountainous Nuristan province and raged throughout the day, is likely to fuel the debate in Washington over the direction of the troubled eight-year war.

It was the heaviest U.S. loss of life in a single battle since July 2008, when nine American soldiers were killed in a raid on an outpost in Wanat in the same province.

Gen. Stanley McChrystal, the top U.S. and NATO commander in Afghanistan, plans to shift U.S. troops away from remote outposts that are difficult to defend and move them into more heavily populated areas as part of his new strategy to focus on protecting Afghan civilians.

U.S. troops used artillery, helicopter gunships and airstrikes Saturday to repel the attackers, inflicting “heavy enemy casualties,” according to a NATO statement. Fighting persisted in the area Sunday, U.S. and Afghan officials said.

The Taliban claimed responsibility for the attack. NATO spokesman Brig. Gen. Eric Tremblay said the assailants included a mix of “tribal militias,” Taliban and fighters loyal to Sirajudin Haqqani, an al-Qaida-linked militant based in sanctuaries in the tribal areas of Pakistan near the Afghan border.

Afghan authorities said the hostile force included fighters who had been driven out of the Swat Valley of neighboring Pakistan after a Pakistani military offensive there last spring.

“This was a complex attack in a difficult area,” U.S. Col. Randy George, the area commander, said in a statement. “Both the U.S. and Afghan soldiers fought bravely together.”

Details of the attack remained unclear Sunday and there were conflicting reports of Afghan losses due to poor communications in the area, located just 20 miles from the Pakistani border and about 150 miles from Kabul.

A NATO statement said the attacks were launched from a mosque and a nearby village on opposite sides of a hill, which included the two outposts — one mostly American position on the summit and another mostly Afghan police garrison on a lower slope.

NATO said eight Americans and two Afghan security troopers were killed.

An Afghan military official, speaking on condition of anonymity because of security issues, said three Afghan soldiers and one policeman had been killed in two days of fighting. He also said at least seven Afghan army soldiers were missing and feared captured.