KIEV - Some 100,000 Ukrainians chanting “Revolution!” swarmed a central Kiev square Sunday in a mass call for early elections meant to punish President Viktor Yanukovych for rejecting a historic EU pact.

The crowd, with many waving the gold-and-blue flag of the European Union, took control of Kiev’s iconic Independence Square and steered a bulldozer within striking distance of metal police barricades protecting the presidential adminstration building on a nearby sidestreet.

Footage broadcast by a private Ukraine television station also showed a few dozen people breaking into an empty Kiev city hall building and reading speeches demanding an immediate break in relations with Russia.

“The government and president must resign,” world boxing champion turned opposition leader Vitali Klitschko said to loud cheers and cries of “Yes!” “A revolution is starting in Ukraine,” added nationalist opposition leader Oleh Tyagnybok. “We are now launching a national strike,” he said in dramatic scenes aired live on television stations in both Ukraine and Russia. The ex-Soviet nation of 46 million was thrown into its deepest crisis since the 2004 pro-democracy Orange Revolution when Yanukovych snubbed EU leaders at a Vilnius summit on Friday and opted to keep Ukraine aligned with its former master Russia.

The government’s decision - first announced a week before the EU meeting - sparked mass demonstrations that turned violent in the early hours of Saturday when hundreds of rubber baton-wielding police drove about 1,000 protesters from Kiev’s focal Independence Square.

A few hundred of them spent the night at the nearby Mikhailovsky Monastery, burning wood in metal barrels to ward off the freezing temperature and receiving food from the monastery’s monks.

The protesters vowed to form a “national resistance task force” and called for early elections as well daily rallies aimed at blocking the entrance to the Ukrainian government seat.

Sunday’s demonstration was held in defiance of a sudden ban imposed late Saturday by Kiev’s main administrative court on all protests on the square and its surrounding streets until January 7.

But dozens of police officers quickly gave way when the crowd overwhelmed the area and knocked down metal barriers surrounding a huge Christmas tree that authorities had put up.AFP reporters estimated the size of Sunday’s crowd at about 100,000 people while some protest leaders and Ukrainian media put the figure even higher. There was no immediate official police estimate.

Saturday’s police crackdown sparked a new round of Western condemnation of the Ukrainian government but was met with notable silence by Russian President Vladimir Putin’s Kremlin.

US State Department spokeswoman Jen Psaki called on Kiev authorities to respect Ukrainians’ right to free expression and assembly, which are “fundamental to a healthy democracy”.

German Foreign Minister Guido Westerwelle also issued a strongly-worded statement saying: “I vigorously call on the Ukrainian government to ensure freedom of assembly.”

Ukraine’s leaders appeared to be taking steps to distance themselves from the violence by announcing a formal probe to identify and punish those responsible for sparking Saturday’s unrest in which more than 30 people were hurt. Kiev’s police chief submitted his resignation at a Sunday meeting during which Interior Minister Vitaliy Zakharchenko vowed to make sure his force acted with “tolerance”.

Yanukovych added in televised comments aimed directly at the opposition that Ukraine had already chosen its “historic path” by committing itself to closer EU relations.

Yet he also stressed that these closer ties with the 28-nation bloc would come only when Ukraine was treated as “an equal partner that is respected and whose wishes are taken into account.”

Kiev’s nuanced approach in which it seeks favour from both Moscow and Brussels was underscored yet again Sunday when the government said Yanukovych would soon travel to Russia to sign a new “cooperation roadmap”.

Jailed former prime minister Yulia Tymoshenko - a top Yanukovych rival whose release was a condition for signing the EU deal - called on Ukrainians to press ahead with their fight. The opposition has drawn up a list of demands that includes the immediate ouster of both Yanukovych and his government as well as early elections.

The Ukrainian parliament’s opposition leader Arseniy Yatsenyuk urged supporters to blockade the Ukrainian government building when it resumes work on Monday. The new “national resistance task force” meanwhile was aimed at organising an indefinite nationwide strike.