Rebels launch 'intense' attacks on Ukraine government troops: Kiev military

KIEV (Reuters) - Pro-Russian rebels launched new attacks against Ukrainian government positions on Sunday, the Kiev army said, as Western countries threatened more sanctions against Moscow for backing a new separatist offensive.

Recent days have seen the worst fighting in eastern Ukraine since a September ceasefire, restarting a war that has already killed more than 5,000 people.

Rebels have announced an offensive and launched an assault on Saturday on Mariupol, a major port of 500,000 people, where Kiev said thirty civilians were killed by shelling.

Kiev officials said the offensive continued on Sunday along other areas in the front, which winds through two eastern provinces partially controlled by the separatists.

"Rebels are attacking the positions of anti-terrorist operation troops extremely intensively, using artillery, mortars, grenade launchers, tanks," military spokesman Andriy Lysenko said in a televised briefing.

He said four Ukrainian servicemen had been killed and 17 injured in the past 24 hours and reported that rebel attacks on the town of Debaltseve, northeast of separatist-held Donetsk, had been particularly fierce.

"Because of constant shelling in the past few days, there are dead and injured among local residents. Around 60 homes have been destroyed or damaged," he said without giving a figure for the number of casualties.

Rebel leader Alexander Zakharchenko said on Saturday the separatists planned to encircle Debaltseve, which has a population of around 26,000.

Western countries say the rebels, who are fighting for the independence of territory they call "New Russia", have launched their offensive with the direct military support of Russian troops on the ground. Moscow denies it is involved.

Following an emergency meeting, Ukraine's national security council said it would adopt a series of measures to counter "the Russian threat and manifestations of terrorism supported by Russia," it said in a statement.

Last week Ukrainian President Petro Poroshenko said Russia had 9,000 troops stationed in his country.

On Sunday he said de-escalating the conflict was the priority for the Kiev government and reaffirmed his commitment to the September peace deal signed in the Belarussian capital Minsk.

(Reporting by Natalia Zinets; Writing by Alessandra Prentice; Editing by Peter Graff)