A top Ukrainian protest leader said Saturday that the opposition is ready to lead the country, but that he would not immediately accept an invitation by embattled President Viktor Yanukovich's to become prime minister.
Arseniy Yatsenyuk's statement on Saturday came several hours after Yanukovich offered the premiership in what was seen as a move to quell protests, which have grown increasingly violent in recent days.
But the concession did little to appease demonstrators. New violence erupted in Kiev overnight, as a large crowd attacked a government conference hall where police were stationed inside.
Protestors were seen throwing firebombs into the Ukrainian House building and setting off fireworks. Police responded with tear gas. Although the crowd created a corridor at the building's entrance apparently for police to leave, none were seen coming out.
The violence flared just hours after Yatsenyuk rebuffed Yanukovich's offer.
Accepting could have tarred Yatsenyuk among protesters as a sell-out, but rejecting it would make him appear unwilling to seek a way out of the crisis short of getting everything the opposition wants.
Meanwhile fellow opposition leader Vitaly Klitschko, a former international boxing champion, was offered the deputy prime minister responsible for humanitarian issues under the presidential concessions.
But he later told German newspaper Bild am Sonntag: "This was a poisoned offer by Yanukovich to divide our protest movement. We will keep on negotiating and continue to demand early elections."
Ukraine's opposition protesters have said that they want Yanukovich to resign, early elections, and the repeal of harsh anti-protest laws that set off clashes between demonstrators and police over the past week.
Yanukovich called for a special session of parliament Tuesday and said it could discuss repealing those laws.
"Tuesday is judgment day," Yatsenyuk told a large crowd of protesters on Independence Square. "We do not believe any single word. We believe only actions and results."
Before Yanukovich made his offer, anti-government protesters on Saturday seized a regional administration building, and officials said that two police officers who had allegedly been held there by demonstrators were freed. But protesters said they had never held the officers in the first place. One protest leader called the claim a provocation aimed at justifying a crackdown.
Interior Minister Vitaly Zakharchenko, one of the government figures who protesters have heavily criticized, said the two officers were released with the help of negotiations by foreign embassies. He said they had been hospitalized, but did not give details of how they were allegedly abused.
Zakharchenko earlier said the officers were seized by volunteer security guards at the protest gatherings in Kiev. But the commandant of the corps, Mykhailo Blavatsky, told The Associated Press that no police had been seized.
"The authorities are looking for a pretext to break up the Maidan and creating all kinds of provocations," he said, referring to the main square of Kiev where around-the-clock protests have been going on for nearly two months. "Capturing a policeman would only give the authorities reason to go on the attack, and we don't need that."
Zakharchenko's claim and an earlier statement that a third captured officer had been released and was in serious condition in a hospital raised fears that police were preparing to break up the protest.
"We will consider those who remain on the Maidan and in captured buildings to be extremist groups. In the event that danger arises, and radicals go into action, we will be obliged to use force," Zakharchenko said.
Demonstrations that started in late November to protest President Viktor Yanukovich's decision to shelve a long-awaited agreement to deepen ties with the European Union had been mostly peaceful until a week ago, when radical factions enraged by new laws to crack down on protests clashed violently with police.
The clashes and the spread of unrest beyond the Ukrainian capital suggest that the government could be losing control of much of the country.
According to Nina L. Khrushcheva, a graduate professor of international affairs at New York-based university The New School, Ukraine decending into anarchy isn't out of the realm of possibility.
She believes the best move for opposition leaders is to take positions offered in the government. Refusing to do so could lead to further strife and disorganization, she said.
"If they have no government, then it's a recipe for chaos," she said, adding: "They may end up being another Syria or another Egypt. And having that in the middle of Europe is a disaster for all."
Over the past five days, police have arrested dozens of injured protesters being treated at hospitals, said Al Jazeera's Sue Turton, reporting from Kiev. When asked about why patients are being removed from hospitals, neither doctors nor police officers would comment.
In response, opposition leaders have started to urge police to resign. In at least one police station, officers gave up their posts to join protesters.
The Kiev city hall, which demonstrators have claimed as their headquarters for two months, is only a few hundred yards from Independence Square, the site of protracted clashes between police and protesters over the past week and the location of a tent camp that was erected in early December.
Protesters seized another building Friday amid a shaky truce. An attempt by police to storm the demonstration headquarters would likely set off new clashes.
Protesters on Saturday morning seized the headquarters of the energy ministry, but left it several hours later. Energy Minister Eduard Stavitskiy was quoted by the Unian news agency as saying that all the country's nuclear power facilities were put on high alert after the seizure.
In Vinnitsya, about 110 miles southwest of Kiev, hundreds of demonstrators stormed the local administration building, Ukrainian news agencies said. Until the past week, the protests had been centered in Kiev with only smaller demonstrations elsewhere, but since the Kiev clashes began Sunday, a score of local government buildings have been seized in the country's west, where support for Yanukovich is thin.
Yanukovich has refused protesters' demands to resign and call early elections, offering only minor concessions to the opposition Friday. Violent clashes then resumed in Kiev's government district, with protesters pelting rocks and fire bombs at police, who responded with stun grenades, tear gas and rubber bullets.
On Saturday morning, the clash site was tense, with demonstrators milling about, many of them bearing clubs, metal rods and large sticks. They watched as black smoke billowed from a barricade of burning tires, but there was no violence.
Interior Minister Zakharchenko said other countries "must not close their eyes" to rising extremism in Ukraine. The country has come under wide criticism from the West during the protests, particularly after at least two demonstrators died of gunshot wounds in clashes this week.
"The events of recent days in the Ukrainian capital showed that our attempts to peacefully resolve the conflict without resorting to forceful opposition remain futile," Zakharchenko said.
Yanukovich has called a special parliament session for Tuesday.
He said on Friday that the session would consider a government reshuffle, amnesty for many of the arrested protesters and changing recently passed harsh new laws cracking down on protests.
The new laws were a critical factor in prompting the last week's violence, in contrast to the determined peacefulness of most of the previous weeks of protests.
The holding company of Rinat Akhmetov, a powerful tycoon whose support has been important to Yanukovich, on Saturday issued a statement calling for a peaceful resolution of the crisis, saying, "The most important thing is that the route of force will not find an exit."
Al Jazeera and The Associated Press