Ukraine's opposition on Saturday called for early elections after riot police brutally broke up a pro-Europe rally, leaving dozens injured in a crackdown on protests against President Viktor Yanukovych's refusal to salvage a key EU deal.
Opposition parties also said they would form a "national resistance task force" and call a countrywide strike, as several hundred protesters took shelter in a nearby church following the pre-dawn swoop by baton-wielding police officers.
Some 10,000 protesters rallied on Saturday, matching Friday's turnout, calling for the president's resignation after he left an EU summit in Vilnius without signing a key political and free trade deal.
The agreement would have brought Ukraine closer to the bloc and away from historical master Moscow, which put pressure on the ex-Soviet country -- still reliant on Russia for energy and as an export market -- to turn its back on the deal with Brussels.
The government announced it was halting work to sign the accord a week before the summit, sparking the biggest protests in Ukraine since the 2004 pro-West Orange Revolution.
On Saturday, the protesters gathered outside the tall walls of the ancient golden-domed Mikhailovsky cathedral where several hundred injured protesters had been given sanctuary.
"We can and should remove these authorities," world boxing champion and opposition leader Vitali Klitschko told the rally.
Top opposition leader Arseniy Yatsenyuk added the opposition had met EU ambassadors on Saturday.
"We've had a very serious conversation," he told the crowd. "We are hoping for a clear and tough reaction of the Western world."
Some protesters were waving blue and yellow Ukrainian flags, while others sported the red and black banners of the ultra-nationalist Ukrainian Insurgent Army.
Drivers in passing cars also honked in solidarity.
The opposition is calling a major demonstration for Sunday in a key test of the protest movement's ability to sustain momentum.
Thousands have been taking to the streets for daily protests across the country since Kiev abruptly announced on November 21 that it would not be signing the EU deal.
At 4:00 am Saturday, riot police moved in to disperse about 1,000 protesters who remained on the Independence square, swinging batons and dragging the demonstrators on the ground.
"Dozens wounded, dozens arrested. Ukraine has not seen anything like this before," opposition lawmaker Andriy Shevchenko said on Twitter.
Medics said more than 30 people had sought treatment, while a police spokeswoman told AFP more than 30 protesters had been detained for hooliganism and resisting police.
After the protest violence, the opposition demanded that authorities call early presidential and parliamentary polls.
"We have made a joint decision to form a national resistance task force and have begun preparing for an all-Ukrainian national strike," Yatsenyuk told an emergency briefing earlier Friday.
On Saturday police and metal barriers surrounded the square which had been cleared of discarded clothes, plastic bottles and plates.
The stage from which opposition leaders had addressed their supporters was taken down and tractors hauled away pro-EU placards and metal barrels.
The US condemned the use of violence against peaceful protesters, urging the Ukrainian government to "respect the rights of civil society."
EU foreign policy chief Catherine Ashton and Enlargement Commissioner Stefan Fuele echoed the condemnation. They also called on authorities to carry out a probe into the events.
There was no immediate comment from Yanukovych's office but Prime Minister Mykola Azarov said on Facebook he was "deeply outraged and concerned" by the events and promised a thorough investigation.
Leaders of Orthodox churches in Ukraine also condemned the violence against the demonstrators.
Taking shelter in church
Protester Maria Chalykh told AFP that riot police had moved in suddenly on the demonstrators.
"We were dancing, jumping and crying out peaceful slogans," she said.
"They started beating everyone indiscriminately. They beat everyone, the elderly, girls, even a child. His entire face was covered in blood," said the 17-year-old student. "Everyone shouted, cried, some people fainted."
Chalykh said that the Berkut (Golden eagle) riot police dragged people, kicked and swore at them.
She herself lost consciousness and only came around in an ambulance, she said.
Several hundred protesters, some with bloodstains on their clothes and flags, were offered shelter in the Mikhailovsky Orthodox monastery where monks gave them first aid.
"Everyone abandoned us," Igor Mitrov from the southern Crimean peninsula told AFP at the cathedral. "We do not know what to do next."
Kiev police spokeswoman Olga Bilyk said police cleared the square in order to start preparations for the New Year's holidays.
"When equipment approached the Maidan, the protesters started behaving in an aggressive manner and ignored police requests," she told AFP.
Jailed former prime minister Yulia Tymoshenko called on Ukrainians to press ahead with the fight against the government.
"I am calling on all of Ukraine's mothers and fathers not to leave the authorities' actions unanswered," she said in a statement read out by her daughter Evgenia.