Ukraine's jailed former Prime Minister Yulia Tymoshenko declared a hunger strike to press the government to sign a deal with the European Union amidst large-scale protests in Kiev.

Tymoshenko's lawyer, Serhiy Vlasenko, announced the decision Monday at a protest against the government's move to shelve the association and trade deal with the EU and forge closer ties with Russian instead.

An activist of the Ukrainian Opposition Party holds a poster with a photo of former Ukrainian Prime Minister Yulia Tymoshenko during a rally in Kiev, Ukraine, Thursday, Nov. 7, 2013. (Sergei Chuzavkov/Associated Press)

The EU considers Tymoshenko's imprisonment politically motivated and has warned it will not sign the deal unless Tymoshenko is freed. It is not her first hunger strike.

Ukraine' President Viktor Yanukovych has resisted the EU pressure, apparently fearing that Tymoshenko, whom he closely defeated in the 2010 vote, would challenge him again in the 2015 presidential election.

Tymoshenko ready to talk

Last week, Tymoshenko said in an open letter she was ready to ask the EU to drop the demand for her release if it can help persuade Yanukovych to sign the deal.

Yanukovych's government suddenly announced last week that it was halting its plans to sign the political association and trade deal with the 28-member EU in order to boost ties with Russia instead, after several years of preparations and firm promises from Yanukovych that he would sign it.

Hundreds of demonstrators clashed with riot police, throwing traffic cones and other objects at officers wearing gas masks and armed with rubber batons. The opposition said that one protester was injured.

Biggest protest since Orange Revolution

The scuffle follows protests in the heart of Kiev Sunday that was the biggest since the 2004 Orange Revolution that helped bring a pro-Western government to power.

European Commission President Jose Manuel Barroso and European Council President Herman Van Rompuy said in a statement Monday that the deal remains on the table. They criticized Russia for pressuring its neighbor, arguing that the agreement with Ukraine was conceived as "a win-win where we all stand to gain."

The Ukrainian government argues that the nation's economy would not survive a trade war with Russia, after the Kremlin imposed restrictions on Ukrainian exports and warned Kiev it would raise new trade barriers if it goes ahead with the EU deal

Opposition protesters clash with riot police in front of the Ukrainian Cabinet of Ministers in Kiev, Ukraine, Monday, Nov. 25, 2013. (Andrew Kravchenko/Associated Press)

Kiev also blamed the International Monetary Fund for imposing stringent conditions for a bailout loan to aid its struggling economy.

Protests continued overnight, with demonstrators camping out in tents on a central square. Round-the-clock rallies are planned for the rest of the week in a bid to urge Yanukovych to change his mind and sign the agreement at a summit in Lithuania on Friday. But it is unclear how much patience the government will have with the protesters. Prime Minister Mykola Azarov hinted that authorities would not tolerate the kind of 24/7 sit-in that brought Orange Revolution leaders to power in 2004.

EU aid dubbed ‘a pittance’

Yakunovych's office has not commented on the protests, but his ally Azarov staunchly defended the turn toward Moscow Sunday evening. In an interview with Ukraine's ICTV channel Azarov snubbed the economic aid offered by the EU as "a pittance" and said that Moscow, by contrast, has offered a discount for Russian natural gas imports, which Ukraine has been seeking for several years.

Dozens of protesters were rallying on European Square in downtown Kiev Monday morning, dancing to patriotic music blaring from loudspeakers, hiding from rain under umbrellas and waving Ukrainian and EU flags.

"I have been to Europe and seen how people live there. I want my children and grandchildren to have a normal life," said Halyna Polychuk, 50, a retired store manager who came to Kiev from the western city of Ivano-Frankivsk to join the demonstrations.