The 28-nation EU said it would impose travel bans on and free assets of those it considers responsible for the bloody violence, and also ban the export of equipment likely to be used for repression in Ukraine, the New York Times reported. But the exact extent of the sanctions remained in flux as EU foreign ministers appeared intent on giving the government of President Viktor Yanukovych some room to find a way to resolve the crisis, the newspaper said.
"The scale of the implementation of that will depend on developments to come, and of course we want to see success in government and opposition working together in order to bring about a peaceful situation and a peaceful and democratic settlement," British Foreign Minister William Hague told reporters in Brussels.
An hours-old truce between the Ukraine government and the opposition disintegrated Thursday, with protest medical officials reporting more than 100 people died in fighting with police, CNN reported. Three police officers were killed, the Interior Ministry said.
If the death toll is authenticated, Thursday would be the deadliest day in Ukraine since protests began in November. Protesters said at least 500 people were injured.
The international community strongly criticized Yanukovych's government over violence Tuesday and Wednesday in which 26 people died. Several countries, including the United States, warned of consequences for the government's actions and of possible sanctions.
"We are outraged by the images of Ukrainian security forces firing automatic weapons on their own people," said the White House in a statement. "We urge President Yanukovych to immediately withdraw his security forces from downtown Kiev and to respect the right of peaceful protest, and we urge protesters to express themselves peacefully."
The trigger for Thursday's clashes wasn't clear, CNN said, adding that its crews at the scene reported a group of protesters threw rocks and Molotov cocktails at security forces as the forces were moving away from the area. Police responded with gunshots.
Both sides blamed each other.
"Protesters broke the truce," Yanukovych's office said in a statement. "The opposition used the negotiation period to buy time, to mobilize and get weapons to protesters."
Olga Bogomolets, a doctor treating protesters, accused government forces of shooting to kill, saying she had treated 13 people she thinks were targeted by "professional snipers."
"They were shot directly to their hearts, their brain and to their neck," she told CNN. "They didn't give any chance to doctors, for us, to save lives."
CNN said it could not independently confirm Bogomolets' claim.
German Chancellor Angela Merkel's office said she had urged Yanukovych to accept European help in talks with the anti-government opposition.
The White House statement said the United States will work with its European allies "to hold those responsible for violence accountable and to help the Ukrainian people get a unified and independent Ukraine back on the path to a better future."
On Wednesday, Obama administration imposed visa travel bans on some 20 senior Ukrainian government members.
Russia's state-supported news agency RIA Novosti reported Foreign Ministry spokesman Aleksandr Lukashevich as criticizing Western diplomatic efforts.
"The ongoing attempts to obtrusively intervene from outside, threat with sanctions or trying to influence the situation in any other ways are inappropriate and can't lead to anything good but can only aggravate the confrontation," Lukashevich was quoted as saying.
The latest violence came just hours after Yanukovych declared in a statement he had agreed to a truce with key opposition leaders and was ready to start negotiations "with the aim of ending bloodshed and stabilizing the situation in the state in the interests of social peace."
Though Yanukovych said he had agreed to a truce, Ukraine's Defense Ministry said it was prepared to call in the military to restore order.
"Military servants of the armed forces of Ukraine might be used in anti-terrorist operations on the territory of Ukraine," a ministry statement said.
It was unclear how the military could be legally brought in for a domestic, police-type mission without authorities first declaring a state of emergency, the New York Times said.
The White House statement Thursday called on the Ukrainian military "not to get involved in a conflict that can and should be resolved by political means."
"The use of force will not resolve the crisis -- clear steps must be taken to stop the violence and initiate meaningful dialogue that reduces tension and addresses the grievances of the Ukrainian people," the statement said.
Before declaring the truce, Yanukovych fired Chief of Armed Forces Gen. Volodymyr Zaman and replaced him in that post with Navy chief Vice Admiral Yuriy Ilyin.
Zaman was widely seen as pro-European, the Times said.
Protesters are seeking the restoration of Ukraine's 2004 constitution, which they said would solve the country's political crisis. The ruling Party of Regions said it would review a law reforming the constitution, but refused to return to a previous version.
Thousands of demonstrators have flocked to Kiev's Independence Square since November, when Yanukovych reversed a decision to sign a trade and association deal with the European Union and instead turned toward Russia.
An anti-protest law later went into effect, inflaming the thousands of demonstrators filling the streets to protest the anti-free speech measures.