KIEV, Ukraine _ A deadly confrontation in the Ukrainian capital eased, at least temporarily, late Wednesday when the government announced that it had reached a truce with opposition protesters who continue to occupy a square in central Kiev.

The truce announcement came after a tense day in which the government warned that it was launching an “anti-terrorist operation” and President Viktor Yanukovich replaced the armed forces chief, who reportedly had been reluctant to use the army against civilian protesters.

Yanukovich and three opposition leaders agreed on a truce after a round of urgent talks in the presidential administration building in downtown Kiev, opposition leader Arseny Yatsenyuk told reporters.

“The positive news is that the planned storming and the sweeping (of the Independence Square opposition camp) have been canceled,” Yatsenyuk said after emerging from the meeting. “A truce has been called which sets the beginning for negotiations to stabilize the situation.”

The news, however, was not met with much enthusiasm in the square, where the sounds of stun grenades used by police continued from time to time even after the truce was called. Riot police units were not being withdrawn from the area near the square.

At least one opposition leader said his group would not observe the truce.

Earlier, busloads of police and Interior Ministry troops had poured into central Kiev, where thousands of protesters remained in the smoky expanse of Independence Square. World leaders, including President Barack Obama, urgently called on both sides to step back from the brink _ words that may ultimately have been heeded.

Violence Tuesday and Wednesday claimed more than 25 lives and left hundreds injured in the worst clashes since protests began in November. Western-leaning opposition forces are furious with Yanukovich for spurning an economic pact with the European Union in favor of closer ties with neighboring Russia, which shares a common culture with Ukraine but also has a long history of dominating it.

The West has pleaded with Ukraine to find a path to compromise, but Yanukovich appeared to take another tack Wednesday, when his security chief issued a strongly worded warning on his agency’s web site.

“What is happening today is a conscious use of violence by way of arson, murder, hostage-taking and intimidation … for the sake of pursuing criminal goals,” Alexander Yakimenko said in a statement published on the Ukraine Security Service website. “All of that with the use of firearms. These are not just signs of terrorism but concrete terrorist acts.

“By their actions, radical and extremist groups bear a real threat to lives of millions of Ukrainians,” his statement said.

Hours later, Ukraine’s UNIAN news agency said Yanukovich had fired the armed forces chief, Vladimir Zamana, and replaced him with another commander, Yuri Ilyin.

“The sudden switch can be explained by Yanukovich’s desire to use the army in combating the growing protests,” Vadim Karasyov, head of the Institute of Global Strategies, a Kiev-based think tank, said in an interview. “Zamana has recently hesitated … to get involved in helping to defuse the political crisis.”

As dusk set over Independence Square, several thousand protesters armed with sticks, stones and Molotov cocktails faced hundreds of police equipped with tear gas and stun grenades, water cannons and shotguns firing rubber bullets.

Firefighters continued efforts to extinguish a blaze consuming the Trade Unions building, which had served as the opposition headquarters until it caught fire during clashes Tuesday night.

Police and the opposition blamed each other for the fire.

The Ukraine Security Service statement about terrorists came on the heels of Yanukovich’s speech earlier in the day in which he laid responsibility for the violence and casualties on the opposition, which he accused of a coup attempt.

Radical opposition activists, especially in western regions of Ukraine, have alarmed the government in recent days with such tactics as attacking military units and capturing a weapons storehouse in the Ivano-Frankivsk region, and taking the family of a governor hostage in the town of Lutsk.

Moreover, though most casualties in Kiev have been among demonstrators, police have had significant losses. The Interior Ministry said the most recent violence had left 10 police officers dead and 350 hospitalized with injuries, 74 of them with gunshot wounds.

The instability in Ukraine, a country of 45 million people that is roughly the size of France, has sent tremors through the international community, and led to talk of sanctions.

The European Union summoned its foreign ministers to an emergency meeting in Brussels on Thursday to consider “targeted sanctions” against those who ordered Tuesday night’s crackdown on protesters.

In Paris, French Foreign Minister Laurent Fabius said he and the German and Polish foreign ministers will visit Ukraine on Thursday morning before traveling on to Brussels. It was necessary to consider whether “those who are responsible for these acts should continue to avoid sanctions,” he said.

The U.S. State Department banned 20 Ukrainian civilians from obtaining U.S. visas. A senior official, speaking on condition of anonymity in order to discuss sensitive matters, said the list included the “full chain of command” responsible for the deadly clashes, although he would not name them.

Additionally, Ben Rhodes, a deputy national security adviser, said the United States was looking for ways to exert its influence. “We have a tool kit for doing that that includes sanctions,” he said.

Obama, on an official trip to Mexico, did not mention sanctions but sent a warning.

“I want to be very clear as we work through these next several days in Ukraine that we’re going to be watching closely, and we expect the Ukrainian government to show restraint, to not resort to violence in dealing with peaceful protesters,” Obama said. “We’ve also said we expect peaceful protesters to remain peaceful, and we’ll be monitoring very closely the situation, recognizing that with our European partners and the international community there will be consequences if people step over the line.”

Obama later welcomed news of a truce, saying that if implemented “it could provide space for the sides to resolve their disagreements peacefully.”

Moscow had indicated that it was ready to back any resolute action on the part of Ukraine’s leadership.

“The blame (for the crisis) unconditionally lies with extremists who all these weeks and months have been trying to push Ukraine to a use-of-force scenario,” Russian Foreign Minister Sergei Lavrov said Wednesday. “A serious measure of responsibility lies with the opposition leaders who rejected compromise.”

(Tribune Washington Bureau reporter Christi Parsons in Toluca, Mexico, Los Angeles Times reporter Tracy Wilkinson in Mexico City and Kathleen Hennessey of the Tribune Washington Bureau in Washington contributed to this report.)

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