A Russian television journalist has been shot dead in eastern Ukraine despite a shaky truce between separatist rebels and Ukrainian forces, the reporter's employer said on Monday.

Anatoly Klyan, a 68-year-old cameraman, was among a group of Russian journalists on a reporting trip in the separatist city of Donetsk, Channel One said.

"Once on site, shots rang out from the soldiers' side. Anatoly Klyan was mortally wounded in the stomach," the channel said.

Russian national television stressed that the journalist - the third media worker to die in eastern Ukraine over the past two weeks - was killed despite a truce that was due to expire late on Monday night.

Several other television crews, including those from pro-Kremlin LifeNews and liberal Ren TV, were also shot at but escaped unhurt, Channel One said.

Demanding that the perpetrators be punished, the Russian Foreign Ministry said in a statement, "Ukrainian forces clearly don't want a de-escalation of the conflict in the country's east and are obstructing the already fragile truce."

With the cease-fire due to end late on Monday, the leaders of France, Germany, Russia and Ukraine were expected to take part in a four-way telephone conversation to seek a way forward.

French President Francois Hollande and German Chancellor Angela Merkel were expected to apply further pressure on Russian President Vladimir Putin to withdraw support for the separatist uprising in eastern Ukraine.

The last-minute talks follow a two-hour conversation between the four on Sunday in which Merkel and Hollande reiterated a warning from the EU that it could slap punishing sanctions on Moscow on Monday if Putin did not explicitly pressure pro-Kremlin rebels to stop fighting.

The two European heads and Putin agree on the need to extend a cease-fire that they say is a key first step toward ending 13 weeks of bloodshed that has claimed some 450 lives.

Ukraine's national security council said on Monday it would make a decision on whether to extend the cease-fire before it expired.

Embattled Ukrainian President Petro Poroshenko is coming under growing public pressure to launch a full-scale assault, with some 500 people protesting against the cease-fire outside his office on Sunday.

"We have to declare martial law in the east and clean out the region as quickly as possible," Igor, an ex-soldier who has volunteered to fight the insurgents, told AFP.

"Now we have enough resources to do this, but if the authorities delay then the rebels will get reinforcements and this disease will spread," he said.