KABUL, Jan. 29 (Xinhua) -- Gunmen attacked a military university in Kabul, capital of Afghanistan early on Monday, triggering explosions and gun fight, with unknown casualties, sources and witnesses said.

The fighting started roughly at 05:00 a.m. local time when one assailant detonated explosives in the front gate of the Marshal Fahim National Defense University. The second group of militants tried to breach and enter the compound, an eye witness told Xinhua.

"The nature of the first blast was similar to a car bombing as it caused panic among the residents. The whole place has now been sealed off," he said.

The university is located in Charrah-i-Qambar in Police District 5 of the city.

The attackers were using guns and Rocket Propelled Grenades (RPGs) in the predawn clash.

"The exchange of fire and sporadic explosions were ongoing at around 07:30 in the morning as personnel of army's Kabul 111 Division, in charge of providing security for the facility, was responding to the attack," a security source told Xinhua anonymously.

The gunmen also fired several shots on nearby apartment buildings which give home to families of military officers.

"We still cannot provide details on causalities. There is fear of possible causalities," the source added.

Further details about the incident are still forthcoming amid the absence of any official statement.

The capital city with a population of nearly 5 million has been hit by series of terror attacks over the past couple of years.

On Saturday, about 103 people were killed and 235 injured in a massive car bombing in central Kabul.