The Ukrainian Security Service has opened a criminal investigation into an explosion on a school sports ground in Donetsk on Wednesday evening which killed two teenagers and injured four others, National Security and Defense Council spokesman Andriy Lysenko said.

"An explosion of an artillery round fired from territory controlled by gunmen at the sports ground of school No. 63 killed two teenagers and injured four others. Intelligence indicates that the round flew from the side of the city of Makiyivka, where terrorists groups are stationed. The Security Service has already opened a criminal case into this fact," Lysenko said at a news conference in Kyiv on Thursday.

Ukraine has repeatedly pointed out that illegal armed groups regularly fire artillery at residential neighborhoods and then accuse Ukrainian government forces of this, and the Wednesday tragedy is one of such examples, Lysenko said.

"We have said repeatedly that terrorists shell residential neighborhoods, trying to prove that this was done by Ukrainian troops and set the local population against the Ukrainian security forces by such provocations," Lysenko said.

"This was a planned action," he said.