Russian President Vladimir Putin and his Ukrainian counterpart Petro Poroshenko have discussed a possible ceasefire, the Kremlin said tonight.

"The issue of possible ceasefire in the area of a military operation in Ukraine's southeast has been touched upon," the Kremlin said after the talks.

Mr Putin expressed concern over the deaths of two Russian television journalists in Ukraine today.

He stressed the importance of ensuring safety of reporters working in Ukraine, the Kremlin said, adding Mr Poroshenko has vowed to conduct an investigation.

The Russian state television journalists were killed after they were shelled in clashes between Ukrainian forces and pro-Russian separatists near the eastern city of Luhansk, according to Russian media.

Sound engineer Anton Voloshin was killed at the scene and correspondent Igor Kornelyuk died in hospital.

They came under fire while covering fighting in Ukraine's easternmost province, near the border with Russia, the Rossiya-24 channel said on its website.

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

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

"This death is yet another horrid reminder that not enough is being done to protect journalists who risk their lives reporting from conflict zones in Ukraine," Dunja Mijatovi, OSCE representative on media freedoms, said in a statement.

A third member of the Russian TV crew, cameraman Viktor Denisov, survived the attack on the rebel roadblock where they were filming.

The crack of heavy artillery and Mr Denisov's ragged breathing is audible on the shaky footage he shot of the scene, crouched by a military vehicle.

As smoke clears, a fighter is shown dragging a wounded man off the road into the bushes.

"I got lucky," Mr Denisov told the Russian Life News website. "One of the shells landed on them ... I ran the other way when the area came under fire."

A spokeswoman for separatists in Luhansk said the body of Mr Voloshin, who was initially reported missing by Rossiya-24, had been found at the scene.

"His body, or rather, his remains were found directly at the site of the mortar attack in the village of Metalist," the spokeswoman was quoted by Russian news agencies as saying.

Last month, an Italian photographer and his Russian translator were killed by mortar fire.