Ukraine's interior minister says at least three pro-Russian separatists were killed and 13 wounded in a clash with national guardsmen at a base in the Ukrainian town of Mariupol.
Arsen Avakov says the separatists attacked the base with grenades and gasoline bombs. He said the troops disarmed most of the attackers and arrested 63.
The incident comes as the Russian and Ukrainian foreign ministers get ready for emergency talks in Geneva with U.S. Secretary of State John Kerry and European Union foreign policy chief Catherine Ashton.
A White House spokesman says Kerry will look for any signs Russia is serious about de-escalating the tensions in Ukraine.
Russian President Vladimir Putin said on a television call-in show Thursday that the Geneva talks are really important in the search for a compromise in Ukraine.
Mr. Putin said a democratic process is the only way to bring order back to the country.
He also called it "nonsense" to think there are Russian military units in Ukraine. He said all separatist actions are being carried out by local residents.
U.S. Ambassador Samantha Power told the U.N. Security Council Wednesday there is substantial evidence of Russian involvement in the unrest in eastern Ukraine. She called it a well-orchestrated professional campaign of incitement and sabotage.
Moscow has said it has the right to protect Russian speakers in Ukraine. It accuses the new Ukrainian leadership of being anti-Russian and anti-Semitic and of threatening the rights of pro-Russians.
President Putin said Russia's annexation of Crimea last month was not planned, but a reaction to what he called tangible threats against Russians living there.
But senior U.N. human rights official Ivan Simonvic said earlier that his team found no widespread attacks against ethnic-Russians during two trips to Ukraine in March.