MOSCOW, June 18  -- Russian President Vladimir Putin had asked Ukrainian counterpart Petro Poroshenko to ensure the safety of journalists in a telephone conversation Tuesday, the Kremlin said.

"Putin expressed concern over the tragic death of Russian journalists near Lugansk and drew attention to the necessity of ensuring security of mass media representatives working in the conflict zone in Ukraine," Kremlin spokesman Dmitry Peskov said.

"Poroshenko reassured Putin that he had ordered a thorough investigation be carried out and had taken measures to ensure the security of journalists," he said.

Separately, Russian Prime Minister Dmitry Medvedev offered condolences over the death of the two Russian journalists in eastern Ukraine and accused those "who refer to themselves as authorities" in Ukraine of being responsible for the situation in the country.

Igor Kornelyuk died in hospital, while his colleague Anton Voloshin's body was found later at the scene where the two were hit by mortar fire from Ukrainian troops, according to the All-Russia State Television and Radio Company (VGTRK).

The UN Security Council encouraged "a thorough investigation of all incidents of violence involving journalists," and expressed concern about "reported cases of detention and harassment of journalists covering the crisis in Ukraine," a statement issued Tuesday said.

Last month, 30-year-old Italian photographer Andrea Rocchelli and his translator were killed when they were caught up in fierce fighting in the rebel-held flashpoint of Slaviansk.

The deadly conflict in eastern Ukraine between insurgents and government troops has been raging for nearly two months. Reports of journalists being detained or kidnapped and refugees fleeing have aroused international concern.