(QHA) -

President of Ukraine Petro Poroshenko and Russian President Vladimir Putin have discussed possible ceasefire in eastern Ukraine where Ukrainian forces have been fighting with pro-Russian separatists, RFE/RL reports.

According to the Kremlin, Poroshenko and Russian President Vladimir Putin also discussed the deaths announced earlier on June 17 of two Russian state television journalists.

Russian media reported, that sound engineer Anton Voloshin and correspondent Igor Kornelyuk were killed after they came under fire while covering fighting near the eastern city of Luhansk.

The Russian Foreign Ministry said the deaths demonstrated the "criminal nature" of Ukraine's military operation against pro-Russian rebels and urged authorities in Kyiv to investigate.

The Organization for Security and Cooperation in Europe (OSCE), whose special monitoring Mission is working in eastern Ukraine, echoed the call for a probe into the attack.

Elsewhere, Ukraine said it was treating an explosion on a pipeline carrying Russian gas to the rest of Europe as a possible "act of terrorism."

The Interior Ministry issued a statement which described the blast, which sent a plume of dark smoke high into the sky over central Ukraine, as "the latest attempt by the Russian side to discredit Ukraine as a partner in the gas sector."