Taliban militants have stormed an Afghan army outpost, killing more than a dozen soldiers in an area that is a major infiltration route for insurgents crossing the mountainous border between Afghanistan and Pakistan.
The Taliban are stepping up their attacks this spring, analysts say, as they try to position themselves for power ahead of national elections and the planned withdrawal of most US and other foreign combat troops by the end of 2014.
The persistent violence has undermined confidence in the ability of President Hamid Karzai's forces to take over the country's security.
The attack began at dawn in the Nuri district of Kunar province, a volatile area that serves as a pathway for insurgents travelling to Afghanistan from their sanctuaries in north-west Pakistan. Hostilities have surged as weather improves, allowing easier movement through the remote area.
The militants started by firing 20 rockets at the outpost, which housed about 30 soldiers, said provincial police chief Abdul Habib Sayedkhaili. He said three Afghan soldiers and four Taliban were killed. But Defence Ministry spokesman Mohammad Zahir Azimi said 13 soldiers were killed in the fighting, which lasted about five hours.
Taliban spokesman Zabiullah Mujahid claimed responsibility for the attack and said the insurgents captured the base, seizing ammunition and weapons. He claimed 15 Afghan soldiers died in the attack and that the militant fighters suffered no casualties.
This year's fighting season is being closely watched because Afghan forces have to operate with less support from the international military coalition, making it a test case of their ability to operate independently as US and other foreign troops take on more of an advisory and training role.
Afghanistan now has about 100,000 international troops, including 66,000 from the United States. The US troop total is scheduled to drop to about 32,000 by early next year. The bulk of the reduction is to occur after fighting presumably winds down in the winter.
"The Taliban want to show the international community that they are the power in Afghanistan," said Jawed Kohistani, an Afghan political and military analyst. "Relations between the Afghan government and the international community are not so good, which is good for the Taliban."
He said the militants attacked several small bases housing Afghan units, but only caused casualties at the one in Nuri district. He said 13 Afghan soldiers were killed, but that reinforcements were sent and the Afghan security forces "took the base back fairly quickly and basically pushed the enemy out of the area."