At least eight Afghan soldiers have been killed and several wounded in an attack by Taliban insurgents on a military base in Balkh province, military officials say.
Some reports say the number of troops killed or injured is far higher than initially reported.
The military say that Friday's attack took place near a mosque at the base, located in the city of Mazar-e-Sharif.
The Taliban said in a statement that they launched the attack.
The insurgents said they had inflicted heavy casualties on the army.
The Taliban fighters wore army uniforms and drove through military checkpoints before launching the raid, a military spokesman said.
An army commander told the AFP news agency that gunfire at the base could still be heard late on Friday and at least one of several attackers had blown himself up.
The base at Mazar-e-Sharif is home to the Afghan National Army's 209th Corps, responsible for providing security to most of northern Afghanistan, including Kunduz province - which has seen heavy recent fighting.
Several German and other foreign soldiers are reported to be garrisoned there.
Last month about 50 people were reported to have died when militants believed to be from the group known as Islamic State targeted patients and staff at a military hospital in Kabul with guns, grenades and knives.
Also in March the Taliban said they had captured the crucial south Afghan district of Sangin after a year-long battle.