Taliban ambush kills scores of Afghan troops

The Afghan Taliban killed 21 soldiers in an assault Sunday in a remote mountainous region, the Afghan government said. In addition to the 21 dead, six soldiers were missing after the most deadly assault on the security forces in months.

Also Sunday, in a possible blow to U.S. efforts to foster peace talks to end the Afghan conflict, the Taliban said they had suspended efforts to arrange a possible exchange of Taliban and U.S. prisoners due to the "complexity" of the situation.

It was not immediately clear whether the attack in the eastern province of Kunar was related to the suspension of talks on a prisoner swap.

In response to the killings in Kunar, a mountainous region that borders Pakistan and has long been a stronghold of the Taliban, Al-Qaeda, and other armed groups, President Hamid Karzai put off a trip to Sri Lanka.

"The Afghan president is saddened by this tragic incident, and therefore he postponed today's official trip to Sri Lanka," Karzai's office said in a statement.

Government officials said 21 soldiers were killed and three were wounded in the attack on an army checkpoint in Kunar's Ghaziabad district.

The government sent reinforcements to the area where the pre-dawn attack took place, Afghan Defense Ministry spokesman Zahir Azimi said in a news release – but the Taliban appeared to have been waiting for them. The reinforcements "came under enemy attack, and a suicide bomber detonated his explosives near them,” Azimi said.

The Afghan Taliban, in a statement emailed to media, claimed responsibility for the attack. Local officials in Kunar said three attackers were killed.

Sunday's assault was the worst Taliban-perpetrated violence since last September, when the Taliban attacked a convoy of Afghan forces in relatively peaceful northern Badakhshan province, killing at least 18.

The attack took place as U.S. and NATO forces withdraw from Afghanistan ahead of a year-end deadline, shifting the bulk of the fight against Taliban and other armed groups to Afghan soldiers.

While Afghanistan's police and army are seen as having made big strides in their capabilities, doubts remain about whether they can keep the Taliban at bay, especially in remote areas like Ghaziabad.

It remains unclear if the United States and allied nations will keep a small force in Afghanistan after 2014 to support Afghan forces and go after Al-Qaeda, due to Karzai's refusal so far to sign a pact authorizing a future troop presence.

Al Jazeera and wire services