SLOVYANSK, Ukraine (CNN) -- Foreign ministers from across Europe and beyond are meeting Tuesday in Vienna, Austria, with the worsening crisis in Ukraine at the top of the agenda.
The Council of Europe meeting comes amid a dramatic escalation of violence in Ukraine.
Ukrainian security forces battled pro-Russian militants in the eastern flashpoint city of Slovyansk on Monday as Kiev tackled the gunmen who have overrun the region.
Ukraine's Interior Ministry said four people were killed and nearly 30 injured in the city. It quoted local residents as saying the attackers had shot at residential buildings and set them on fire. Militants blamed Ukrainian forces for the civilian casualties.
Both Russia and Ukraine are among the 47 member states of the Council of Europe.
After a morning session devoted to issues around democracy and human rights, the foreign ministers are expected to discuss the situation in Ukraine over a working lunch.
Unrest has spiraled in Ukraine since street protests forced out pro-Moscow President Viktor Yanukovych in February. The interim government scheduled presidential elections this month but pro-Russian activists in the eastern part of the country refuse to accept Kiev's authority and want greater autonomy.
Many in the West fear Russian President Vladimir Putin is fomenting trouble in order to increase his influence and justify a possible incursion in defense of Russian speakers in the region.
Speaking on French TV station BFMTV on Tuesday, French President Francois Hollande spelled out what is at stake in Ukraine.
"The main goal we have is that the presidential election should be held in Ukraine on May 25," he said. "Otherwise, there will be chaos and civil war. Vladimir Putin wishes today that this election does not take place."
Amid the unrest in eastern Ukraine, flights into Donetsk Airport were halted Tuesday.
A notice on the website for Donetsk Airport on Tuesday stated that "by order of State Aviation Authority of Ukraine ... arrival and departure of all aircraft from Donetsk airport has been temporarily suspended."
Calls by CNN to the Donetsk Airport press office confirmed the closure. There was no information as to how long it would last.
A number of administrative buildings in the city of Donetsk have been seized by armed pro-Russian groups.
But it was the rebel stronghold of Slovyansk that was the focus of efforts Monday by government forces to regain control from the militants.
Military gains were evident on the main highway into the city as the security forces moved in. A CNN team on the ground saw a substantial number of militants bolster their defensive positions and checkpoints inside the city. One civilian car was hit in the fighting, its exterior damaged by bullet holes.
At a local hospital, the CNN team saw several people injured from the heavy clashes. One woman had been shot in the head, probably in a crossfire, and two pro-Russian militants were also brought in.
The Ukrainian Defense Ministry said a military helicopter was shot down "during a combat mission and patrolling in the area" of Slovyansk on Monday, but the pilots survived after it crashed into a river. They were later rescued.
The pro-Russian separatists have reportedly seized government buildings in nearly a dozen cities and towns.
Kiev authorities describe the separatists as "terrorists." But the rebels say they are defending Russian-speaking areas of the east against Ukrainian "fascists" trying to root out Russian influence in the country.
In a statement Monday, Russia's Foreign Ministry accused the Kiev government of "continuing a war against the people of their own country."
"We again urge the Kiev organizers of terror against their own people to come to their senses, stop the bloodshed, withdraw troops and sit down, finally, at the negotiating table to start a normal dialogue on ways to resolve the political crisis," the ministry said.
Many experts say Russia may be provoking unrest in eastern Ukraine to justify an incursion.
CNN's Nick Paton Walsh reported from Slovyansk and Laura Smith-Spark wrote from London. CNN's Andrew Carey, Marie-Louise Gumuchian and Yon Pomrenze and journalists Lena Kasharkovain and Laura Akhoun contributed to this report.
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