Taliban fighters have attacked the police headquarters in the northern Afghan city of Pul-e-Khumri.
A suicide bomber started the assault, and more attackers then opened fire. Further clashes followed.
Hospital sources say at least 40 people have lost their lives or have been seriously injured.
The Taliban carries out frequent attacks on Afghan forces and now control more territory than any point since their toppling in 2001.
The militants have been holding peace talks with a US envoy in Qatar since October to end the long-running conflict.
An Afghan interior ministry spokesman said two militants have been killed in the latest attack and the rest are under siege from national forces.
The Taliban claimed the attack in a statement.