The Ukrainian Prosecutor General's Office has reported the updated number of National Guard servicemen killed in an accident on the Kyiv-Dovzhansky road in Donetsk region on Monday night.

"It has been established by now that the tragic accident killed 12 servicemen and injured another 21. Casualty reports are being constantly updated," it said on Tuesday afternoon.

The Main Military Prosecutor's Office is probing the road accident under part 2, article 415 of the Ukrainian Criminal Code (a motoring offense). Causes and circumstances of the incident are being studied.

The Prosecutor General's Office heads are personally controlling progress of the investigation.

The Office said earlier that 13 officers died and 21 were injured in the road accident, while the Interior Ministry said the accident killed 12 officers.

A KrAZ truck and a Bohdan bus of the Ukrainian army collided in the army operation zone in eastern Ukraine killing 12 servicemen and injuring another 21, the Ukrainian Interior Ministry said earlier. The collision happened on Monday in bad weather during a rotation of volunteers and contract servicemen of the Ukrainian National Guard in the army operation zone.

The injured servicemen were taken to hospital in Artemivsk. They are being given aid, provided with medicines and evacuated to hospitals of Kharkiv and other hospitals of Ukraine, the ministry said.

In the words of deputy head of the Artemivsk district healthcare department Olena Myronova, four injured servicemen stayed at the Artemivsk hospital and 17 were moved to Kharkiv. "They have combined injuries. The soldiers are in a grave condition," she told the 112 Ukraine channel over the phone on Tuesday.

The media said the road accident happened near the village of Mynkovka in Donetsk region.