Heavy gunfire and explosions have been heard at a military academy in the Afghan capital, Kabul, reports BBC.
The Marshal Fahim National Defense University came under attack early Monday morning, reports said.
It comes days after the deadliest bombing for months hit Kabul when an ambulance packed with explosives killed at least 100 people.
Islamic State and the Taliban have recently carried out attacks in the city.
Several explosions were heard, as well as small arms fire, as the attack began at about 05:00 local time (00:30 GMT), the BBC's Mahfouz Zubaide reported from Kabul.
Security forces have blocked off all roads in the area, Tolo news agency said.
There have been no reports of casualties so far.
The ambulance attack on Saturday, took place just one week after another attack on a Kabul hotel killed 22 people - mostly foreigners. The Taliban said it had carried out both attacks.
Afghan military institutions are frequently targeted by militants.
In October 2017, 15 military cadets were killed in an explosion outside the Marshal Fahim military academy, which is located west of the Kabul city centre.