A huge explosion was heard across the city about 01:25 local time on Monday (20:55 GMT Sunday).
A compound housing foreign contractors in the Afghan capital, Kabul, has come under attack from Taliban fighters.
Reports said it was caused by a lorry bomb at the North Gate compound, and the Taliban says several of its fighters fought their way inside.
Police are engaged in a gun battle with the attackers, with one policeman and one militant killed and a second policeman has been injured.
North Gate is a heavily guarded compound, which was attacked by militants three years ago.
Power in parts of Kabul was briefly cut off shortly after the explosion.
