Editor's Note: Watch a live stream of the protests in Kiev, Ukraine.
KIEV, Ukraine (AP) -- Ukraine's protest leaders and the president they aim to oust called a truce Wednesday, just hours after the military raised fears of a widespread crackdown with a vow to defeat "terrorists" responsible for seizing weapons and burning down buildings.
The two sides agreed to negotiate in an effort to end the violence that left at least 26 people dead and more than 400 injured on Tuesday. Protesters say the casualty toll is substantially higher.
The intense clashes between police and protesters led President Viktor Yanukovych to declare that the military would take part in a "national anti-terrorist operation." The parameters weren't specified, but the military's involvement and Yanukovych's appointment of a new military chief of staff fueled new worries.
As protective fires blazed around the tent camp in Kiev for a second night and protesters defending it showed no signs of yielding, Yanukovych met with top opposition leaders. A statement on his website said they had agreed on a truce and negotiations.
Vitali Klitschko, a leader of the protests that have sought to keep Ukraine open to Europe and out of a close alliance with Russia, said Yanukovych assured them that police would not storm the protesters' encampment on Kiev's Independence Square, according to the Interfax news agency.
The brief statement on the president's website did not give details of what terms a truce would entail or how it would be implemented. Nor did it specify how the negotiations would be conducted or give an indication of how they would be different from previous meetings of the president and the opposition leaders.
Perhaps crucially, there was no immediate indication of whether radical elements among the protesters would observe the truce or be mollified by the prospect of negotiations.
Although the initial weeks of protests were determinedly peaceful, radicals helped drive an outburst of clashes with police in January in which at least three people died. And the day of violence on Tuesday -- the worst in nearly three months of anti-government protests that have paralyzed Kiev -- may have radicalized many more.
The two sides are locked in a battle over the identity of this nation of 46 million, whose loyalties are divided between Russia and the West. The protests began in late November after Yanukovych turned away from a long-anticipated deal for closer ties with the European Union.
After Yanukovych shelved the agreement with the EU, Russia announced a $15 billion bailout for Ukraine, whose economy is in tatters.
Political and diplomatic maneuvering has continued, with both Moscow and the West eager to gain influence over this former Soviet republic. Three EU foreign ministers -- from Germany, France and Poland -- were heading to Kiev on Thursday to speak with both sides before an emergency EU meeting in Brussels to consider sanctions against those responsible for the recent violence in Ukraine.
President Barack Obama also stepped in to condemn the violence, warning Wednesday "there will be consequences" for Ukraine if it continues. The U.S. has raised the prospect of joining with the EU to impose sanctions against Ukraine.
On a visit to Mexico, Obama said the Ukrainian military should not step into a situation that civilians should resolve and added that the U.S. holds Ukraine's government primarily responsible for dealing with peaceful protesters appropriately.
Russia's Foreign Ministry, in turn, described the violence as an attempted coup and even used the phrase "brown revolution," an allusion to the Nazi rise to power in Germany in 1933. The ministry said Russia would use "all our influence to restore peace and calm."
In Kiev, Ukraine's top security agency accused protesters Wednesday of seizing hundreds of firearms from its offices and announced a nationwide anti-terrorist operation to restore order.
Demonstrators, meanwhile, forced their way into the main post office on Kiev's Independence Square, also known as the Maidan, after a nearby building they had previously occupied was burned down in fierce, fiery clashes late Tuesday with riot police. Thousands of activists armed with fire bombs and rocks had defended the square, a key symbol of the protests.
"The revolution has turned into a war with the authorities," Vasyl Oleksenko, a retired geologist from central Ukraine, said Wednesday. "We must fight this bloody, criminal leadership. We must fight for our country, our Ukraine!"
Before the truce was announced the bad blood was running so high it has fueled fears the nation could be sliding toward a messy breakup. While most people in the country's western regions resent Yanukovych, he enjoys strong support in the mostly Russian-speaking eastern and southern regions, where many want strong ties with Russia.