Ukraine's government said on Sunday it was sending security forces into the eastern
city of Slaviansk where pro-Russian militants have seized control in what Kiev describes as an act of aggression by the
Any operation to dislodge the armed militants risks tipping the stand-off into a new, dangerous phase because Moscow has
Interior Minister Arsen Avakov said security units from across the country had been brought in to launch an "anti-terrorist
operation" to re-assert Kiev's control in Slaviansk.
A Reuters reporter in the city, about 150 km (90 miles) from the Ukraine-Russia border, said two military helicopters were
flying over the town's police headquarters where militants were holed up.
"Pass this on to all civilians: they should leave the centre of town, not come out of their apartments, and not go near the
windows," Avakov wrote on his Facebook page.
In the nearby town of Kramatorsk, militants exchanged gunfire with police late on Saturday, though there was no confirmation
any one had been hurt.
Novosti Donbass, a local Internet news site, said that government forces had taken down two rebel barricades at entry points
into Slaviansk, but there was no independent confirmation of this.
Residents in the town did not appear to have heeded the appeal by Avakov and families were out on the streets on their normal
Relations between Russia and the West are at their most fraught since the end of the Cold War, the result of a row over
Ukraine that began when the Moscow-backed president was pushed out, and Moscow annexed Ukraine's Crimean peninsula.
In Washington, the White House expressed concern that the seizures of public buildings in eastern Ukraine could
be a prelude
to a Russian military incursion, though Moscow has strenuously denied any such intention.
"We call on President (Vladimir) Putin and his government to cease all efforts to destabilize Ukraine, and we caution against
further military intervention," said Laura Lucas Magnuson, spokeswoman for the White House National Security Council.
U.S. Vice President Joe Biden will travel to Kiev on April 22, becoming the most senior U.S. official to visit the country
since the crisis began there.
Moscow justified sending its military into Crimea, on Ukraine's southern tip, by saying the Russian population there was
under threat, and some in Western governments believe the Kremlin is preparing a similar scenario for eastern Ukraine.
Russian Foreign Minister Sergei Lavrov has denied any such intentions and said instead it was Ukraine's Western-leaning
government, viewed by the Kremlin as illegitimate, that was stoking the tensions.
Any use of force against Russian speakers "would undermine the potential for cooperation" between Moscow and Western powers
over Ukraine, Lavrov said in a statement after a telephone call with his U.S. opposite number John Kerry.
United Nations Secretary-General Ban ki-Moon said in a statement he was deeply concerned about the deteriorating situation in
eastern Ukraine and "the growing potential for violent clashes".
KIEV'S SHAKY CONTROL
The crisis over Ukraine could trigger a "gas war", disrupting supplies of Russian natural gas to customers across Europe.
Moscow has said it may be forced to sever deliveries to Ukraine - the transit route for much of Europe's gas - unless Kiev
settles its debts.
For now though the focus of the crisis was in eastern Ukraine, the country's industrial heartland where many people feel a
close affinity with neighbouring Russia.
NATO says Russian armed forces are massing on Ukraine's eastern border, while Moscow says they are on normal manoeuvres.
On Saturday, in what had the look of a coordinated action, pro-Russian militants, some of them armed, seized public buildings
in several towns, challenging Kiev's already shaky control over the region.
In Kramatorsk, about 15 km south of Slaviansk, gunmen seized the police headquarters after a shootout with police, a Reuters
Novosti Donbass, a local Internet news site, said armed men had also thrown up barricades at a military airport there while
others continued to occupy the town council building as well as the police headquarters.
The attackers were a well-organised unit of over 20 men, wearing matching military fatigues and carrying automatic weapons,
who had arrived by bus. Video footage showed the men taking orders from a commander. Their identity was unclear.
Their level of discipline and equipment was in contrast to the groups who have occupied buildings so far in Ukraine. They
have been mostly civilians formed into informal militias with mismatched uniforms.
Ukrainian police appeared powerless to intervene, and it was not clear if local security forces were still taking orders from
Kiev. The police chief for the Donetsk region, which includes Slaviansk, resigned after pro-Russian protesters picketed his
In Slaviansk, militants blocking the road leading into the city from the north set fire to tyres and trees, hoping the smoke
would hamper any operation by government forces.
By the side of one road leading into the city, a group of women were praying with a priest. Not far away, a group of about 12
armed men in combat fatigues, helmets and balaclavas and carrying automatic weapons appeared to be monitoring people on the
"We want to join Russia. We would be very grateful if Russia helps us," said a gunman in the centre of Slaviansk who gave his
name as Alexander, wearing camouflage fatigues and a black balaclava mask. "We will stand until victory. Honestly, it's not
scary for me to die for freedom."
Ukrainian commentator Sergei Leshchenko said the burst of activity by pro-Russian groups was an attempt by the Kremlin to
secure a strong negotiating position before international talks about Ukraine.
Representatives of Russia, Ukraine, the United States and the European Union are due to meet in Geneva on Thursday for the
Russia is expected to argue for a revamp of Ukraine's constitution to give a large degree of autonomy to eastern Ukraine,
something Kiev and its Western backers reject.
come to the talks with the position that 'Donetsk and several neighbouring regions are already ours - now let's
talk about federalisation'," said Leshchenko, a commentator with the Ukrainska Pravda newspaper.
(Additional reporting by Conor Humphries in Kiev and Richard Balmforth and Alessandra Prentice in Moscow; Writing by
Christian Lowe; Editing by David Stamp)