This post is being updated as the day continues.
Just hours after a truce was declared, deadly clashes between anti-government protesters and security forces broke out again in Ukraine's capital.
By the end of Thursday in Kiev, more than 20 civilians had been killed, Reuters reported. Those deaths followed some 25 fatalities earlier in the week.
But the day's toll may have been even higher: CNN reported being told by "the head of the protesters' medical service" that 100 people had died Thursday and another 500 were injured.
The newly intensified crisis led a Ukrainian athlete to abandon her Olympic quest Thursday.
"Bogdana Matsotska says she will withdraw Friday from the slalom, her best event at the Winter Games," NPR's Corey Flintoff reports. "Matsotska says she doesn't want to participate when people in her country are dying."
Earlier today, there was word in Kiev that Ukraine's Interior ministry said 67 police officers had been "captured" by protesters. The BBC's Gabriel Gatehouse, though, said protesters had told him "they took 30 police captive this morning. Others said to have surrendered. Not clear where they are now."
NPR's team in Kiev "saw protesters surround eight of the young officers and escort them to safety," as Soraya Sarhaddi Nelson reported for All Things Considered.
The European Union is attempting to intervene. The Polish, German and French foreign ministers were in Kiev today to meet with President Viktor Yanukovych, Soraya says. She added that sanctions could be announced as soon as Friday.
Soraya also says that "there are new signs that Yanukovych's grip on power is weakening. The mayor of Kiev and nearly a dozen other officials belonging to the ruling Party of Regions announced they are quitting their party."
The White House blamed Ukraine's government for the latest carnage.
"We are outraged by the images of Ukrainian security forces firing automatic weapons on their own people," press secretary Jay Carney said in a statement released to reporters. "We urge President Yanukovych to immediately withdraw his security forces ... and to respect the right of peaceful protest, and we urge protesters to express themselves peacefully. We urge the Ukrainian military not to get involved in a conflict that can and should be resolved by political means. ... The United States will work with our European allies to hold those responsible for violence accountable."
From the city's Independence Square, NPR's Soraya Sarhaddi Nelson reported earlier today that it was a scene of "absolute chaos." She saw numerous people carried away on stretchers — one person completely covered by a sheet. Small explosions can be heard. Protest leaders were warning of snipers on rooftops. The opposition appears to have retaken control of the October Palace, a historic building that's now a cultural center. Smoke was rising over the city.
The protesters, Soraya said, say police forces and "thugs" who support Yanukovych never observed the truce that was announced last night.
Yanukovych's office, though, released a statement blaming the opposition for Thursday's deadly violence. It reads, in part:
"Radical protesters ... launched an offensive on the law enforcement officials using firearms despite the declared truce. Assurances of opposition leaders regarding the necessity of truce and restoration of dialogue turned out only a maneuver to play for time and mobilize arming of rebels. ...
"All attempts of the government to establish dialogue and resolve the conflict peacefully were ignored by rebels. They launched an offensive. They act in organized armed groups, use firearms, including sniper rifles, they shoot to kill. ..."
President Obama, as The Guardian reports, has had critical words about Russian President Vladimir Putin's role in the crisis. Russia, Obama said Wednesday, still views the world through a "Cold War chessboard" and needs to support the people of Ukraine in their effort to secure basic freedoms.
The U.S. has also said it will not issue travel visas to 20 senior Ukrainian officials.
Russia opposes sanctions against the Yanukovych government.
Britain's foreign ministry said it has summoned Ukraine's ambassador to the U.K. to a meeting.
As we've reported before, the anti-Yanukovych protests that have been raging for weeks were sparked in part by the president's rejection of a pending trade treaty with the European Union and his embrace of more aid from Russia. Protesters have also been drawn into the streets to demonstrate against government corruption.
We'll be updating on the news from Kiev.