DONETSK, January 22. /TASS/. The law enforcement agencies of the self-proclaimed Donetsk People’s Republic are investigating Thursday morning’s shelling of a tram stop in Donetsk, which killed at least 13 and left 20 injured, the Donetsk Republic Defence Ministry’s spokesman, Eduard Basurin, has told TASS.

The immediate cause of the lethal explosion or the type of the explosive device has not been identified yet. The number of casualties is unclear, too.

“Groups of diversionists are detained in Donetsk now and then. This work is in progress. But it is too early to say who is to blame for the crime,” Basurin said.

The shelling of a tram stop in Kuprin Street in Donetsk at 08:30 Thursday morning was reported to have killed 13 and injured 20 others. It's suspected that the mortar attack was mounted from a minivan. The attack set fire to a trolley bus and a car.

Doctors say many of the injured are in grave condition. People who were near the scene of the attack at the moment keep coming to medics for first aid.

The head of the self-proclaimed republic, Alexandr Zakharchenko, went to inspect the site himself.

Witnesses say a total of five shots were fired. Comprehensive checks are underway in the city. Police are searching all vehicles passing by. A minivan carrying a mortar is being looked for.

Donetsk is a target for systematic bombardments. Local residents say one of the Ukrainian military’s main targets is the city’s Machine-Building Plant in the Leninsky district.