KIEV, Ukraine (AP) -- Protesters in Ukraine's capital extinguished burning barricades shielding them from the police on Thursday, enforcing a tenuous peace as an ultimatum issued by the opposition to the president was set to expire with no sign of compromise.
The fragile truce came after three main opposition leaders urged protesters late Wednesday to refrain from violence for 24 hours until their ultimatum to President Viktor Yanukovych expired. They demanded that he dismiss the government, call early elections, and scrap harsh anti-protest legislation that triggered violence at a demonstration on Sunday.
Opposition leader Vitali Klitschko dove behind the wall of black smoke engulfing much of downtown Kiev on Thursday, pleading with both police and protesters to uphold the peace until the ultimatum expires Thursday evening.
At Klitschko's request, protesters extinguished the burning tires that sent thick clouds of putrid smoke toward police lines.
The largely peaceful protests against Yanukovych's decision to shun the European Union and turn toward Moscow in November descended into violence on Sunday when demonstrators, angered by last week's passage of repressive laws intended to stifle protests, marched on official buildings. For days protesters hurled fire bombs and stones at police, who retaliated with stun grenades, tear gas and rubber bullets.
On Wednesday, riot police beat and shot at protesters, volunteer medics and journalists, resulting in the deaths of two demonstrators -- the first casualties of the clashes. The opposition contended as many as five people died.
The Interior Ministry said Thursday that 73 people have been detained, 52 of them being investigated for "mass riots" -- a recently created criminal charge that carries a prison sentence of up to eight years. Allegations that activists have been abducted and even tortured by police have spread.
The United States has responded by revoking the visas of Ukrainian officials linked to violence and threatened more sanctions.
Chancellor Angela Merkel said Germany doesn't think this is the time to consider sanctions against the Ukrainian government, adding that the current priority is "ensuring that channels of communication are opened up and that the Ukrainian government complies with its obligations to secure fundamental democratic rights."
"We are extremely concerned -- not just concerned, appalled -- about the way in which laws have been pushed through that raise questions over these fundamental freedoms," Merkel said.
EU Commission President Jose Manuel Barroso said that if the situation in Ukraine does not stabilize, the EU "would assess possible consequences in its relationship," according to spokesman Olivier Bailly.
Barroso also said he had received assurances from Yanukovych that he did not foresee the need for imposing a state of emergency in Ukraine.
Russia in turn has accused the West of meddling in Ukraine's affairs.
"We feel regret and indignation about the obvious foreign interference in the developments in Kiev," Russian President Vladimir Putin's spokesman Dmitry Peskov told the daily Komsomolskaya Pravda in an interview published Thursday.
Former Soviet President Mikhail Gorbachev released a letter to Putin and President Barack Obama prodding them to help broker talks to end the crisis. "The situation is such that without help, without assistance of authoritative representatives of our two countries it may lead to a catastrophe," Gorbachev said in the letter, excerpts of which were carried by the Interfax news agency.
Tensions remained high in Kiev, as protesters said they would give peace a chance -- but not for long.
"We're ready to wait so that new victims don't appear," said 30-year-old Anatoly Lovchenko. "But if the government doesn't listen to our demands, we'll start up again."
The three main opposition leaders, who addressed the crowds in the square after meeting the president on Wednesday vowed to lead the demonstrators in battles with police, if their demands are not met. If Yanukovych doesn't concede, "tomorrow we will go forward together. And if it's a bullet in the forehead, then it's a bullet in the forehead, but in an honest, fair and brave way," declared one of them, Arseniy Yatsenyuk.
Raf Casert in Brussels and Vladimir Isachenkov contributed in Moscow contributed to this report.