Investigators of the Security Service of Ukraine (SBU) have established the involvement of regular servicemen of the Russian Armed Forces in a rocket attack on the Skhidny residential district of Mariupol on January 24, 2015, which killed 31 people and injured 117 more, SBU Chief Vasyl Hrytsak has said.

"During the investigation conducted by our investigators and operatives, it was established and documented that this crime had been committed by regular Russian servicemen. This terrorist attack was carried out by two regular missile divisions of the Russian Armed Forces. From Russian territory the operation was directly led by Chief of Missile Forces and Artillery of the Southern Military District of the Russian Armed Forces Major-General Stepan Yaroshchuk and in the temporarily occupied Donetsk the shelling was directed by Colonel of the Russian Armed Forces Alexander Tsaplyuk with the call sign 'Gorets'," he said at a briefing in Kyiv on Monday.

He said that the SBU would transfer to the International Court of Justice (ICJ) part of the materials on the events in Mariupol in 2015, in particular, intercepted negotiations.

According to him, during the investigation the SBU established that the actions of reactive battalions were coordinated out by Russian Armed Forces Lieutenant Colonel Maksim Vlasov with the call sign "Yugra."

"The investigation established the participation in these shelling of the 200th Pechenga Separate Motor Rifle Brigade and the 2nd Guards Tamanskaya Motor Rifle division," Hrytsak said.

He stressed that SBU operatives and investigators had recorded and documented "every minute of events, from the moment when these two divisions crossed the Ukrainian-Russian border and until they left for their positions."

He also said that the final memorandum of evidence as part of Ukraine's lawsuit to the International Court of Justice should be submitted by mid-June this year.

"The evidence is really thorough. You know that in January 2017, Ukraine filed a lawsuit with the International Court of Justice and, in accordance with all the rules, if I'm not mistaken, we must file a final memorandum of evidence before June 12 or 14, in particular, on crimes committed by regular personnel, including servicemen [of the Russian Armed Forces], on Ukrainian territory," Hrytsak said.

He said: "Every proof that will be included in this memorandum is carefully checked, including by international experts, lawyers and only then attached to the files."

"Believe me that this evidence is objective and thorough. A huge amount of work has been done to identify the voices of these people in order to get their personal profiles and so on," Hrytsak said.

He also said that 11 persons, among them four Ukrainian citizens, members of illegal armed groups, as well as seven regular servicemen of the Russian Armed Forces, had been declared suspects as part of the investigation into the artillery attack on Mariupol. All of them have been put on the wanted list.

"We are convinced that such a decision was made by the top military and political leadership of the Russian Federation," he added.