Officials in Ukraine say three anti-government protesters have died in the capital, Kyiv, in new clashes with police.
Two protesters were reported to have gunshot wounds. A medical official said another activist fell to his death at the site of the clashes.
Reports say the police were trying to dismantle a protest camp in Kyiv Wednesday and fired tear gas at demonstrators, who responded by hurling stones and homemade explosives at police.
The U.S. Embassy in Kyiv said in a statement Wednesday that it has revoked the visas of several Ukrainian nationals linked to the violence. The names of those Ukrainians were not released.
The U.S. State Department said it "condemns the increasing violence on the streets of Kyiv, which has led to casualties and the shooting deaths of two protesters" and urges "all sides to immediately de-escalate the situation and refrain from violence."
The State Department said the increased tensions in Ukraine "are a direct consequence of the Ukrainian government's failure to engage in real dialogue and the passage of anti-democratic legislation on January 16."
It also criticized some opposition elements, including the far-right group Right Sector, saying its actions "are inflaming conditions on the streets and undermining the efforts of peaceful protestors."
And European Commission President José Manuel Barroso said Wednesday he was "shocked" by the deaths of protesters in Ukraine. "We deplore in strongest possible terms the use of force and violence, and call on all sides to immediately refrain from it, and start taking steps that would help de-escalate the situation," he said.
Mr. Barroso added that Ukrainian authorities have "the fundamental responsibility" to de-escalate the crisis and "engage in a genuine dialogue with the opposition."
Ukrainian President Viktor Yanukovych met Wednesday with three opposition leaders -- former heavyweight boxer Vitali Klitschko of the Udar party; former economy minister Arseny Yatsenyuk, of jailed former prime minister Yulia Tymoshenko's party; and nationalist Oleh Tiahnybok of the far-right Freedom party.
There was no immediate word on the substance or outcome of that meeting.
On Tuesday, Ukrainian prime minister Mykola Azarov warned the protesters that authorities might use force. Mr. Azarov told Russia's Vesti 24 television that if those he called "provocateurs" did not stop inciting clashes, officials would have no other choice.
The number of injured protesters reached the hundreds by Tuesday, when the anti-government protesters marched through Kyiv for a third straight day. They are protesting President Viktor Yanukovych's November decision to back out of a trade deal with the European Union in favor of closer ties with Russia.
The marchers are also upset over laws recently enacted that tighten restrictions on protests.
Mr. Yanukovych has offered to meet with opposition leaders.
Russian Foreign Minister Sergei Lavrov said Tuesday the situation in Ukraine is "spinning out of control." Lavrov said Tuesday that Russia is doing everything it can to help "stabilize the situation" without meddling in Ukrainian domestic affairs.
In Washington, the U.S. Broadcasting Board of Governors expressed outrage for the bloody police attacks on dozens of journalists in Kyiv, including RFE/RL reporter Dmytro Barkar and cameraman Ihor Iskhakov. They were covering the protests on Monday when they were beaten and struck on the head by members of the elite Berkut police force.