The Taliban stormed an Afghan army outpost in the eastern Kunar province bordering Pakistan early Sunday, killing 20 soldiers and kidnapping seven, an official said.
The volatile border area is dominated by militants who often use improvised explosive devices to target soldiers, but Sunday's attack saw the highest casualty count in a single incident in recent months.
The incident occurred in the Ghaziabad district of Kunar province, provincial governor Shujah-Ul Mulk Jalala told AFP. The Taliban later issued a statement claiming responsibility.
A hunt was underway to release the kidnapped troops, a defence ministry official in Kabul said.
Casualties among Afghan soldiers and police have increased in recent years as they take more responsibility in the fight against insurgents before their Western allies, the US and NATO troops, leave under a US plan by the end of the year.
The governor said "some" of the soldiers in the post were thought to have aided the attackers, though this could not be verified by an independent source and the Taliban did not mention insider help in their statement.
"The Mujahideen overran a key enemy outpost in an assault last night in Ghaziabad," the statement sent by text message to reporters said, terming the Afghan troops "hirelings".
Afghanistan is gripped by a deadly insurgency being waged by remnants of the Taliban since the United States and its NATO allies ousted them from power in 2001.
The rebels' campaign has gathered pace and become more deadly, using a combination of suicide bombings as well as attacks involving multiple individuals storming targets in the middle of big cities and fighting on until they are killed.
The Western-funded Kabul government is desperately trying to strike a peace deal with the Taliban before the withdrawal of foreign troops by the end of this year.
So far, the Taliban have turned down all peace offers by President Hamid Karzai's administration.
Afghanistan is also going to the polls on April 5 to select a successor to President Karzai, as some 55,000 US-led combat troops pull out of the country after 13 years of battling the fierce Taliban insurgency.
Some 8,000-12,000 US soldiers may be deployed on a training and counter-terrorism mission from 2015 if a long-delayed deal is signed with the Afghan government.
