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 Yanukovych’s refusal to salvage a key EU deal.

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 groups also said they would form a "national resistance task force" and call for a countrywide strike, as several hundred protesters took shelter in a nearby church following the pre-dawn swoop by baton-wielding police officers.

A rally of some 10,000 protesters led by top opposition leaders like world boxing champion Vitali Klitschko late Friday had called for the president to step down 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.

Following Friday's rally at Kiev's Independence Square, the epicentre of the 2004 peaceful uprising, around 1,000 protesters remained at the site overnight. 

Riot police moved in on them around 4:00 am local time, swinging batons and dragging protesters on the ground, according to witnesses.

"The Maidan has been brutally mopped up," opposition lawmaker Andriy Shevchenko said on Twitter, using the square's Ukrainian name.

"Dozens wounded, dozens arrested. Ukraine has not seen anything like this before."

Medics said more than 30 people had sought help, while a Kiev police spokeswoman told AFP that 31 protesters had been detained for hooliganism and for resisting police.

On Saturday police and metal barriers surrounded the square strewn with discarded clothes, plastic bottles and plates.

The stage from which opposition leaders had addressed their supporters was taken down and two tractors could be seen hauling away pro-EU placards and barrels protesters had used to light fires to keep themselves warm.

The US embassy in Ukraine condemned the use of violence against peaceful protesters, urging the Ukrainian government to "respect the rights of civil society."

EU chair Lithuania said the use of force against peaceful protesters was "reprehensible."

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.