Kiev resumes military operation in east Ukraine

Ukraine has launched a dawn military operation against pro-Russian separatists in the east of the country as bloody clashes between the two sides show no sign of letting up, Sky News reports.

Interior Minister Arsen Avakov said Ukrainian forces had seized control of a television tower in Kramatorsk, near the rebel stronghold of Slavyansk where there was heavy fighting on Friday.

"We are not stopping," Avakov wrote on his Facebook page, but gave no information on casualties.

The violence came hours after 31 people died after a building in Odessa was set on fire during clashes between protesters.

Police said some people inside the trade union building were overcome by smoke and others were killed jumping from windows as they tried to escape.

Pro-Russian and pro-Kiev activists fought running battles as the southern port city saw some of its worst violence since President Victor Yanukovych was ousted in February.

The fire started as the Kiev government began a major offensive against pro-Russian activists who have seized government buildings in the east of the country.

Russia said it was "outraged" by the day's events in Odessa and denounced the "criminal irresponsibility" of the pro-Western authorities in Kiev.

Russia's foreign ministry said in a statement that it called on Ukraine and its "Western backers to end the anarchy and take responsibility for the Ukranian people".

It added that Moscow viewed the "tragic events" as a sign of Kiev's "criminal irresponsibility".

At an emergency session of the United Nations Security Council, the UK accused Moscow of "breathtaking" hypocrisy over the latest clashes.

The UK's ambassador to the UN Sir Mark Lyall Grant said Russia had "funded, equipped and directed" some of those involved in the insurgency.

"Many" pro-Russian separatists were said to have been killed as the Ukrainian army took control of checkpoints around Slavyansk.

Two Ukrainian soldiers - from the airborne brigade - were also killed as two military helicopters were shot down, acting president Oleksandr Turchynov said.

Russia said Kiev's offensive against the insurgents had "destroyed" the two-week-old Geneva agreement on cooling Ukraine's crisis.

The Ukrainian Security Service said one of the helicopters was shot down with a surface-to-air missile, adding that the sophisticated weapon undermined Russia's claims that Slavyansk was simply under the control of armed locals.