Ukraine in bloody battle to oust pro-Russian gunmen

Slavyansk, Ukraine: Kiev said on Sunday that several had been left "dead and wounded" in fighting to oust pro-Russian gunmen holed up in a police station in the restive east, as Washington warned Moscow to de-escalate the crisis or face the consequences.

Interior Minister Arsen Avakov said both sides had suffered casualties in the offensive in Slavyansk that threatens to further escalate tensions with Russia, which has 40,000 troops massed on Ukraine's eastern border and has warned Kiev against the use of force.

"There are dead and wounded on both sides," Avakov wrote on his Facebook page.

"On our side - an SBU (Ukrainian Security Service) officer. On the side of the separatists - an unidentified number... The separatists have started to protect themselves using human shields."

Helicopters hovered low over the poor mining town, where a thick column of black smoke could be seen, an AFP photographer said.

Residents, mostly women, huddled in the cold under light rain in front of barricades protecting the police building. Armed separatists have also set up a checkpoint at the entry to the town.

Avakov earlier announced that units from "all of the country's force structures" were taking part in the first stiff response from Kiev to the unrest sweeping the volatile eastern part of the country.

He said the gunmen had opened fire on Ukraine's special forces and were "shooting to kill".

With military precision and dressed in unmarked fatigues, unknown gunmen on Saturday launched a series of attacks against security buildings in the tinderbox eastern rust belt.

This came after a week of soaring tensions as pro-Russians demanding greater autonomy, or to join nearby Russia, stepped up protests in the region ahead of May 25 presidential polls.

The protesters refuse to recognise the new pro-Western government in Kiev, which swept to power on the back of bloody winter protests against fallen president Viktor Yanukovych's decision to reject closer ties with the European Union and move closer to Russia.

'Act of aggression'

Moscow has kept up crushing pressure on the new leaders, first seizing Crimea then threatening to cut off gas supplies and trade with the heavily indebted nation all while keeping up a massive military presence along the eastern border.

The West has expressed alarm that Russia is deliberately stoking tension in the heavily Russified east in order to justify a Crimea-style invasion.

"Militants in eastern Ukraine were equipped with Russian weapons and the same uniforms as those worn by Russian forces that invaded Crimea," US ambassador to Kiev Geoffrey Pyatt wrote on Twitter.

Avakov said the events were seen in Kiev as an "act of aggression" by Russia, which has flatly denied any role in the unrest sweeping Ukraine's east.

US Secretary of State John Kerry on Saturday phoned his Russian counterpart Sergei Lavrov and "made clear that if Russia did not take steps to de-escalate in eastern Ukraine and move its troops back from Ukraine's border, there would be additional consequences", a senior State Department official said.

A wave of US sanctions unveiled in March blacklisted officials and businesspeople close to Russian President Vladimir Putin to protest at Moscow's takeover of Crimea.

And on Sunday, France said it would support new sanctions against Moscow if there was a military escalation in Ukraine, speaking on the eve of a meeting of EU foreign ministers in Luxembourg to discuss the crisis.

'Potential for violent clashes'

UN Secretary General Ban Ki-moon late Saturday called on all sides to "exercise maximum restraint" and engage in dialogue to calm a situation that has a "growing potential for violent clashes", a UN statement said.

The volatile situation in the east cast doubt on the planned direct talks between EU and US diplomats and their Moscow and Kiev counterparts in Geneva on Thursday.

Lavrov had warned that if Kiev used force against "residents of the south-east driven to despair", the talks would be in jeopardy.

The latest wave of unrest began when protesters last weekend seized the seat of government in Donetsk, followed by similar actions in Lugansk and Kharkiv.

In Donetsk the protesters heavily fortified the building as they announced the independence of the "Donetsk People's Republic", the flag of which has gone up over newly seized security buildings across the region.

Donetsk protesters fear a loss of their rights to speak Russian, or the collapse of an already depressed economy if their government cuts ties with their close and historical ally.

A charm offensive by embattled Prime Minister Arseniy Yatsenyuk, who has promised to grant more powers to the country's regions and protect the east's right to use the Russian language, is seen as too little, too late.

However despite the unrest, pro-Russian protests have only drawn crowds of a few hundred and local polls have shown that the majority of citizens in the Russian-speaking east would prefer to remain part of Ukraine.

As tensions soared, about 20 pro-Kremlin gunmen seized the Slavyansk police station and later occupied the city's SBU security service building on Saturday.

Similar raids were reported to have taken place in other towns, but they remain unconfirmed.

In Donetsk, a bustling city of one million that was the seat of power of the ousted Yanukovych, about 200 pro-Russian protesters armed with clubs and sticks stormed the city's police headquarters without meeting any resistance.

Police have stepped aside in many similar raids, many of them sporting orange and black Saint George ribbons -- a symbol of Russian heroism in World War II.