Local health officials said 14 people had been killed in the last 24 hours In the Donetsk region.
Kiev said it had taken the town of Lysychansk, northwest of the second separatist bastion of Luhansk.
A spokesman for Ukraine's Security Council said 13 soldiers had been killed in the last 24 hours, taking the total death toll to 325 since the start of fighting against the rebels who say they want independence for the Donbass region.
Yatseniuk, a key interlocutor of the West during much of the turmoil in the country since November, announced he was quitting on Thursday, saying parliament was betraying the people's demands for change by failing to pass legislation.
The move by an ally of former Prime Minister Yulia Tymoshenko could hamstring decision-making as Ukraine struggles to fund a war against pro-Russian rebels and deals with the aftermath of a passenger plane crash.
Oleksander Turchinov, speaker of the parliament, said Yatseniuk's letter of resignation had been sent from government but had yet to be received by parliament.
An aide to President Petro Poroshenko, Oleksander Danilyuk, said the resignation should not hurt what Kiev calls its "anti-terrorist operation" against rebels in eastern Ukraine. Pentagon: The Pentagon said on Friday the transfer of heavy caliber multiple launch rocket systems from Russia to Ukrainian separatists appeared to be imminent, with the arms close enough to the border they could be handed over "potentially today." "We have indications that the Russians intend to supply heavier and more sophisticated multiple launch rocket systems in the very near future," said Army Colonel Steve Warren, a Pentagon spokesman, adding that the weapons were in the over-200mm range. Warren indicated the weapons had been seen getting closer to the border and the Pentagon believed a transfer was imminent and "potentially today." "We believe that they are able to transfer this equipment at any time, at any moment," he said. Positions: Russia said on Friday the United States was trying to influence international opinion through unfounded insinuations and anti-Russian rhetoric over the crisis in Ukraine. "We deny the unfounded public insinuations that State Department Spokeswoman M. Harf repeats day after day," Russia's Foreign Ministry said in a statement on Friday. "In journalistic briefings in previous days she has produced anti-Russian clichs that Washington stubbornly tries to impose on international opinion," the statement said. Harf said at a briefing on Thursday that Russia was firing artillery across the border into Ukraine to target Ukrainian military positions in the conflict against pro-Russian separatists.
REUTERS