SLAVYANSK, Ukraine - Russia warned Monday that Europe's peace was at risk over the escalating crisis in Ukraine, where deadly fighting raged around a flashpoint eastern city and the interim president warned of "war".
European leaders fearing all-out civil war was breaking out on their eastern flank have launched a desperate new peace bid, trying to force Ukraine and Russia to find a negotiated solution before it is too late.
The chairman of the Organisation for Security and Cooperation in Europe, Didier Burkhalter, was due in Moscow on Wednesday amid calls for his group to mediate between Kiev and the separatists in the east.
But events on the grounds were overtaking the diplomatic initiative.
Fierce exchanges of fire were taking place to the east and south of the town of Slavyansk, the epicentre of the armed insurgency, as Ukrainian troops corralled pro-Russian gunmen towards the centre for what could be a devastating showdown.
"They are waging a war on us, on our own territory," Interior Minister Arsen Avakov told reporters as he oversaw the offensive in the combat zone. "My mission is to eliminate the terrorists."
He said there had been deaths in the exchange of fire by small arms and heavy weapons, but did not immediately give a toll for each side.
The advance on Slavyansk was part of a wider military operation in the east to root out the insurgents, who are holding more than a dozen towns and who have declared two autonomous territories around them.
There were concerns also for the south of Ukraine, in the port city of Odessa, which was seething after a deadly day of clashes and a fire last Friday that killed 42 people.
Russia, which denies any hand in the eastern or southern violence, warned in a foreign ministry report on Monday that the unrest in Ukraine was now "fraught with such destructive consequences for Europe's peace, stability and democratic development that it is absolutely necessary to prevent it".
The report accused Ukrainian "ultra-nationalists" - who Moscow claims controls Kiev's government - of rights violations on a "mass" scale.
Earlier Monday, Ukraine's interim president declared that Russian meddling had brought war to his country, and warned that pro-Russian provocateurs might stage violence in Kiev during celebrations on Friday marking the Soviet victory over Nazi Germany in World War II.
"War is in effect being waged against us, and we must be ready to repel this aggression," said Oleksandr Turchynov, who has placed Ukraine's armed forces on combat alert and reintroduced conscription amid fears of a Russian invasion.
On a visit to Odessa on Sunday, Prime Minister Arseniy Yatsenyuk vowed a full investigation into the violence that occurred there last week and blamed what he called the "inefficient" police force.