KIEV   - Jailed Ukrainian opposition leader Yulia Tymoshenko was on hunger strike Tuesday in solidarity with thousands of pro-European protesters outraged with the ex-Soviet state’s shock decision to scrap a key EU pact.

The fiery co-leader of the pro-democracy Orange Revolution in 2004 announced her move in a letter read to some 20,000 supporters who thronged central Kiev on Monday. Organisers expect thousands to turn out on Kiev’s European Square Tuesday evening for a third straight day of protests against President Viktor Yanukovych’s U-turn on the EU accord.

Sporadic clashes have marred the rallies in Kiev and more nationalist parts of western Ukraine, with riot police firing tear gas at demonstrators and protesters hurling street cones and rocks at security personnel.

Dozens of demonstrators fought helmeted police near the government seat in central Kiev on Monday, just after Tymoshenko’s letter was read out to the swarming crowd. “I am announcing an indefinite hunger strike demanding that Yanukovych sign an association and free trade agreement with the EU,” said the jailed former prime minister. “And if Yanukovych does not sign our agreement with the EU on November 29, wipe him off the face of Ukraine through peaceful and constitutional means.”

Protesters have set up two dozen tents in central Kiev where they have been spending the night to make sure police do not close off the square where the largest demonstrations are being held.

Some started makeshift fires in large metal barrels to keep warm from the freezing drizzle and the season’s first sightings of snow.

Two top members of the European Parliament warned Ukraine on Tuesday that it faced “serious consequences” should police continue resorting to the use of force against protestors.

The latest crisis in the nation of 45 million was sparked by the government’s abrupt decision to scrap the planned signature of a historic deal with the EU at a two-day summit in Vilnius starting Thursday.

The U-turn came shortly after Yanukovych held secret talks in Russia with President Vladimir Putin meant to address economic sanctions Moscow planned to slap on Kiev if it signed the EU pact.

These included a threat to impose strict conditions on Russian natural gas deliveries on which Ukraine depends, especially in the winter months.

Yanukovych calls for ‘peace’

The so-called Association Agreement with the EU would have put Ukraine firmly on the path to eventual membership and pulled it out of Russia’s historical orbit.

But Putin sees neighbouring Ukraine — a country known in Russia as the “near abroad” — as a vital member of a rival economic bloc called the Customs Union that already includes Kazakhstan and Belarus.

The 28-nation European bloc has said its offer is “still on the table” and reiterated its criticism of Russia’s intimidation of Ukraine.

Yanukovych late on Monday said his change of mind was based on the dangers economically struggling Ukraine would face if it ruptured its tight trade ties with Russia.

“I want peace and calm in our big Ukrainian family,” the president said in a video statement posted on his website.

Ukraine’s decision to abandon the EU agreement came after parliament repeatedly failed to adopt legislation that would have freed Tymoshenko — a top EU condition for the signing of the deal.

Some analysts believe Yanukovych feels threatened by Tymoshenko and would like to keep her out of politics until he runs for re-election in March 2015 polls.

Tymoshenko was sentenced to seven years in prison in 2011 — shortly after she lost to Yanukovych in bitter 2010 presidential polls — on abuse of power charges that she and the West say were politically motivated.

Yanukovych is still scheduled to travel to Vilnius for the Eastern Partnership summit and some EU leaders appeared to hold out hope that Kiev may yet change its mind.

Poland’s Gazeta Wyborcza newspaper reported on Tuesday the Vilnius summit was also going to adopt a veiled warning to Russia not to interfere in its neighbour’s affairs.

But Putin’s spokesman Dmitry Peskov told the Interfax news agency that “in this case, it is inappropriate to speak of some sort of pressure” being placed by Russia on its neighbour.