Twenty-one soldiers have been killed and six have been captured in Afghanistan.

The attack on an army checkpoint in Kunar took place as US and NATO forces withdraw from the country ahead of a year-end deadline, shifting the bulk of the fight against Taliban and other militants to Afghans.

General Zahir Azimi, spokesman for the Afghan Defence Ministry, described what happened: “This attack was carried out by a lot of domestic and foreign terrorists. As a result of the heavy fighting, a number of the Afghan army soldiers were martyred, some wounded and some are still missing.”

Afghan forces launched an operation to free the captured soldiers.

The Taliban have suspended efforts to arrange a possible exchange of Taliban and US prisoners due to the “complexity” of the situation.

The militant group have claimed responsibility for the attack.

The Afghan president postponed a planned visit to Sri Lanka over the incident.