At least 20 people were killed Thursday in Kiev as fighting between the Ukrainian government and protesters reignited, protesters said. The Interior Ministry said a police officer was among those killed in fighting in the Maidan, or Independence Square, CNN said. A medical representative for the protesters said at least 20 people were dead CNN reported it was unclear what prompted the renewed violence Thursday morning, but as security forces withdrew from the area, protesters pursued them, throwing rocks and Molotov cocktails. Police responded with gunshots. The renewed violence brings the three-day death toll to at least 46, CNN said. The fighting came just hours after Ukrainian President Viktor 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. Yanukovych previously said he did not intend to make such a declaration, and the military had recommended against it, the Times said. But 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. European foreign leaders had called an emergency meeting Thursday in Brussels, though after the morning's violence, it's unclear if the meeting is still on. German Chancellor Angela Merkel, who previously warned harsh sanctions risked deepening the rift between Kiev and the West, said, "We need to plan sanctions that target the perpetrators of violence." All 28 member states must back the sanctions for the EU to enact them. The Obama administration, which Wednesday imposed visa travel bans on some 20 senior Ukrainian government members, said it was considering a wider package of sanctions, possibly in concert with the EU. The government has established police checkpoints around Kiev, shut down subways, imposed restrictions on other forms of public transportation and closed schools, which independent newspaper Ukrayinska Pravda said amounted to a de facto state of emergency. The violence that erupted Tuesday was the worst since the former Soviet republic gained independence in the breakup of the Soviet Union in 1991. 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 deal with the European Union and instead turned toward Russia. An anti-protest law later went into effect, inflaming the protests as thousands of demonstrators filled the streets to protest the anti-free speech measures.