KIEV — Ominous new action by Ukraine’s security forces Monday, including a raid on an opposition party and threats of treason charges, appeared to scuttle an opening for talks between the government and demonstrators, witnesses and opposition figures said.
In a sign of renewed alarm, Vice President Joe Biden and European Commission President Jose Manuel Barroso each made calls to Ukraine’s besieged president, Viktor Yanukovych, to warn him away from unleashing violence on a mass demonstration movement in its third week.
Senior envoys including the European foreign affairs chief, Catherine Ashton, and US Assistant Secretary of State Victoria Nuland were being sent to try to defuse the crisis.
After seeming to lose control of Kiev on Sunday night after a huge rally of hundreds of thousands of people in Independence Square, police forces redeployed on Monday and began efforts to push protesters out of streets near main government buildings.
Battalions of police officers took up positions just outside the square’s perimeter.
Then, on Monday evening, the Ukrainian security service raided the headquarters of the opposition Fatherland Party and seized computer servers.
The party’s parliamentary leader, Arseniy P. Yatsenyuk, is one of the main organizers of the protest movement, which has ballooned in recent days to dominate the streets of Kiev and pressure Yanukovych after he refused to sign a political and trade pact with the European Union.
But the party is best known as the opposition coalition formed by the jailed former prime minister, Yulia V. Tymoshenko, whose release has long been demanded by Western leaders.
“They came without any notice, without any explanations, fully armed,” said Natalia Lysova, a spokeswoman for Fatherland who often accompanies Tymoshenko’s daughter, Evgenia, at public appearances. “They broke the door, took all the servers, and left.”
Lysova said the security officers did not arrest anyone.
A day earlier, the security service issued a curt statement saying that it had opened an investigation into possible treason charges against unnamed politicians.
At a news conference with other protest leaders Monday, Yatsenyuk said he had been summoned for questioning on Tuesday.
Just hours before the raid, Yanukovych had signaled that he would accept a proposal by three predecessors to hold “a national roundtable for finding a compromise” and that initial discussions would begin Tuesday. But any sense that his willingness to negotiate might ease the crisis was quickly erased.
“We understood that this is the way Yanukovych invites us to the roundtable — a few thousands of Interior forces have arrived already, and I received a summon for interrogation from the General Prosecution Office,” Yatsenyuk said.
The raid and police remobilization brought a fresh round of warnings from Western leaders, who reacted in alarm after the security forces violently cracked down on protesters on Nov. 30.
White House officials said Biden pressed Yanukovych to immediately deescalate the crisis and open talks with opposition leaders. And he warned that “violence has no place in a democratic society and is incompatible with our strategic relationship,” according to a White House summary of the leaders’ phone conversation.
Ashton, the European Union’s envoy, was to arrive Tuesday. She had been deeply involved in efforts to draw Ukraine into closer ties with the European Union through the trade deal.
That decision to abandon the wide-ranging trade and political agreement with the European Union left officials in Brussels deeply frustrated and upended years of efforts to draw Kiev into Europe’s orbit and away from Russia’s.
Warning that “anti-European” voices risk reviving old “demons of Europe, like extreme nationalism, like xenophobia,” Barroso, the European Commission president, praised Ukrainian protesters for showing that Europe has positive values.
“If sometimes in Europe some of us have doubts about how important these values are, just look at Ukraine,” he said “Those young people in the streets of Ukraine, with freezing temperatures, are writing the new narrative for Europe.”