Pro-Russia demonstrators Monday defied a government deadline for protesters to vacate occupied buildings in exchange for amnesty, as Ukraine's president threatened a military crackdown.
Dozens of protesters smashed windows of the police headquarters in the eastern Ukrainian city of Horlivka and scuffled with police as they took control of the facility. Video of the confrontation showed an ambulance where injured people were being treated.
The pro-Russian demonstrators, sheltering behind barricades in the occupied buildings, are demanding a referendum on whether to split with Ukraine and join Russia - similar to last month's vote in Crimea.
Ukraine's acting president Oleksandr Turchynov on Monday threatened to launch what he called a "full-scale anti-terrorist operation" against those who have taken over the buildings. The president's office said that in a telephone conversation with United Nations Secretary-General Ban Ki-moon, Mr. Turchynov said Ukraine would welcome the help of the U.N. in such an operation.
Earlier in the day, Mr. Turchynov said he is not against a national referendum on what kind of country Ukraine should be. He said he is certain a majority would support a united and independent Ukraine, possibly giving broader localized rights to the east. He said such a vote could be held at the same time as the May 25 presidential election.
In Moscow, Russian Foreign Minister Sergei Lavrov said Monday he believes Russian-speaking Ukrainians in the eastern part of the country should be part of drafting a new constitution.
Mr. Turchynov has promised amnesty for those who give up their weapons and come out peacefully. But he says he will not let Russia take over eastern Ukraine the way it annexed Crimea.
U.S. Ambassador to Ukraine Geoffrey Pyatt told VOA's Russian service that his greatest fear for the region is that the conflict devolves into greater violence, which the United States does not want.
"You have people in cities across eastern Ukraine, some of them heavily armed with Russian weapons including state-of-the art sniper rifles, Russian inventory automatic machine guns with grenade launchers. These are not peaceful protesters, this is an armed force. And I think there is a real risk that their actions could precipitate greater violence and any bloodshed of course is something that the United States will oppose."
In Luxembourg, European Union foreign ministers threatened Russia with more sanctions, with British Foreign Secretary William Hague warning of consequences for Moscow's behavior in Ukraine.
Russia also came under heavy criticism during an emergency meeting of the United Nations Security Council Sunday night. U.S. Ambassador Samantha Power accused the Russians of "writing and choreographing" the violence in Ukraine.
Top diplomats from Russia, the United States, Ukraine and the European Union are set to hold emergency talks on the crisis April 17 in Geneva. White House officials say U.S. Vice President Joe Biden will travel to Kyiv April 22.
On Monday in Washington, the U.S. officials signed a $1 billion loan guarantee to Ukraine. U.S. Treasury Secretary Jacob Lew said the agreement demonstrates the United States' unwavering commitment to see a stable Ukraine. Ukrainian Finance Minister Oleksandr Shlapak said his country is wrapping up talks with the IMF on a comprehensive economic reform program.
Also Monday, the Pentagon confirmed that a Russian SU-24 fighter aircraft flew at least 12 close-range passes of a U.S. ship in the Black Sea on Saturday. A Pentagon spokesman said the USS Donald Cook was never in danger but called the passes "provocative and unprofessional." U.S. defense officials said the action is part of a pattern of Russia's unwillingness to deescalate with Ukraine.