Poland calls on EU to tighten sanctions against Russia

WARSAW (Reuters) - Polish President Bronislaw Komorowski called on the European Union on Monday to consider imposing tougher sanctions on Russia over an escalation of hostilities in Ukraine.

Pro-Russian separatists, backed by what NATO says is the direct participation of Russian troops, have launched an offensive in eastern and south-eastern Ukraine. Kiev said on Saturday 30 civilians had been killed in shelling of Mariupol, a city on the Sea of Azov.

"The response of the Western world should be very firm," Komorowski told a news conference. "In my opinion the EU response should be to deliberately raise the issue of toughening sanctions against Russia."

After months in which European politicians have debated whether it might be time to start rolling back the sanctions, which are hurting the economies of some member states, the talk now is rather of how to tighten them.

Ambassadors from Ukraine and the 28 NATO allies are to attend a special meeting at Kiev's request on Monday to discuss the new flare-up in fighting in the east of the country, NATO said.

The fighting in eastern Ukraine had mainly died down since a September ceasefire but in recent days the war has returned in full force, with the rebels announcing the effective end of the truce and waging an offensive to expand territory under their control.

Saturday's offensive against Mariupol is particularly worrisome for Kiev. Mariupol is a port city of 500,000 people that is important for Ukraine's grain and steel exports and is also the biggest city still in government hands in the two rebel-dominated eastern provinces.

(Reporting by Pawel Sobczak and Adrian Krajewski; Editing by Matt Robinson and Gareth Jones)