At least 27 army personnel were killed and 57 others were injured in a suicide bomb blast that targeted soldiers inside a mosque in their base in Khost province.
The base is located in eastern Khost province, a stronghold of the Haqqani-linked Taliban group.
Captain Abdullah, a spokesman for the 2nd Regiment of Army in Mandozai district in Khost said the ANA members were busy in Friday prayers when the suicide attack happened at around 1:30 pm Kabul time.
Speaking to AP, Afghan military spokesperson Captain Abdullah said that it still wasn't clear whether the attack was carried out by a suicide bomber or whether a remotely detonated device was used.
No group immediately claimed responsibility for the attack.
It wasn't immediately clear whether the attack was carried out by a suicide bomber, but Khost province is a stronghold of the Taliban-linked Haqqani network.
The Taliban, however, have in the past decried attacks on religious gatherings but have almost daily targeted Afghan military and security forces.