Western powers today launched a desperate last-gasp drive for a diplomatic solution to stop Ukraine sliding into civil war, as fighting spread closer to the Russian border.
The head of the Organisation for Security and Cooperation in Europe, Swiss President Didier Burkhalter, was to meet Russian leader Vladimir Putin after Moscow quashed a German-led plan for new peace talks.
And Britain's Foreign Secretary William Hague held talks in Kiev, as the Western-backed government there stepped up its military offensive to seize back a string of eastern towns and cities under the control of pro-Russian gunmen.
On the ground, local media reported that Ukrainian security forces had "liberated" the town hall in the port city of Mariupol near the Russian border.
Explosions and gunfire were also heard overnight in the flashpoint eastern town of Slavyansk, an AFP reporter there said, as the military advanced on rebel-held positions in the centre of what has become a hotbed of separatist activity.
Authorities there claim to have killed more than 30 rebels in a relentless assault on the city. But they have also lost at least nine personnel and three helicopter gunships in the battle with well-armed separatists.
The Russian flag that used to fly over the town hall has been taken down and rebels said they could either stay in the barricaded building they have held for several weeks or abandon it as the situation demands.
Nearly 90 people have died in less than a week in military operations or clashes between pro-Russians and supporters of Ukrainian unity, leading French President Francois Hollande to warn of "chaos and the risk of civil war".
Germany too has said it fears an all-out military conflict, as Putin weighs whether to launch an invasion with the estimated 40,000 troops he has stationed on the border.
With relations between Moscow and the West plumbing depths not seen since the end of the Cold War, the United States and Russia continued to trade barbs as the clock ticked towards an independence referendum planned in eastern Ukraine on May 11.
US Secretary of State John Kerry dismissed the vote as "bogus" and drew parallels with a referendum in Crimea that was annexed by Russia in March.
