At least eight US soldiers and two Afghans have been killed after their combat outposts in a remote area of eastern Afghanistan came under attack, military officials say.
The troops fought scores of tribal militia fighters for many hours on Saturday after the early morning attack in Nuristan province, Nato's International Security Assistance Force said.
"Coalition forces effectively repelled the attack and inflicted heavy enemy casualties while eight Isaf and two ANSF [Afghan National Security Forces] service members were killed," a statement said on Sunday.
However, a Taliban source said that more than 40 US and Afghan troops were killed in the daylong battle the Kamdesh district.
He claimed that the group had been able to take control of the district following the fighting and had captured 35 Afghan, including a police chief.
Mohammad Farooq, the province's deputy police chief, confirmed that contact had been lost with 19 officers and said it was not clear if they were dead or alive.
Taliban influx
Jamaludin Badar, governor of Nuristan province, said that he had sought more security forces for Kamdesh after operations by the Pakistan military in the Swat valley had driven Taliban fighters into the area and neighbouring Kunar.
"When there are few security forces, this is what happens," he told the Associated Press news agency.
The commander of international forces in the eastern area near the border with Afghanistan praised the efforts of the troops at the outposts, which came under under attack from a nearby mosque and village, Isaf said.
"My heart goes out to the families of those we have lost and to their fellow soldiers who remained to finish the fight," Colonel Randy George said in a statement.
"This was a complex attack in a difficult area. Both the US and Afghan soldiers fought bravely together. I am extremely proud of their professionalism and bravery."
The attack was the deadliest for US forces in Afghanistan since nine soldiers were killed in a battle in Kunar province in July 2008.
New strategy
US forces had already announced plans to pull out of the area as part of a new strategy by General Stanley McChrystal, the commander of US and Nato forces in Afghanistan, to focus on population centres.
"Coalition forces" previously announced plans to depart the area as part of a broader realignment to protect larger populations remains unchanged," Isaf said after Saturday's attack.
McChrystal, who now commands more than 100,000 troops, two-thirds of them American, has requested thousands more to implement the plan, warning that without them, the war will probably be lost.
"We are hearing reports that these troops will have to be sent to the north and the west of the country, relatively peaceful areas until only a few months ago," Al Jazeera's Zeina Khodr, reporting from Kabul, said.
"While most of the recent troop losses were in the traditional areas of fighting in the south and east, the American is now worried about the spread of violence across the country."
Barack Obama, the Us president, has already ordered 21,000 extra troops to Afghanistan this year and is re-evaluating his overall strategy for the region before considering whether to send more.