Hours after being released from prison, former Ukrainian prime minister and opposition icon Yulia Tymoshenko praising the demonstrators killed in violence this week as heroes as she addressed a massive crowd at the protester encampment in Kiev on Saturday.

The 53-year-old Tymoshenko, who suffered severe back problems during her 2½ years in prison, spoke to the crowd of thousands from a wheelchair and appeared close to exhaustion.

But her flair for vivid words was undimmed.

"You are heroes, you are the best thing in Ukraine!" she said of those killed in the violence. The Health Ministry on Saturday said the death toll in clashes between protesters and police that included sniper attacks had reached 82.

"We cannot afford to pardon those who were allowed to send bullets into hearts of our young men," she was quoted by the BBC as saying.

Tymoshenko urged the opponents of Ukrainian President Viktor Yanukovych not to abandon their protests in central Kiev even though parliament has voted to oust him.

She added: "You have no right to leave the Maidan (square)... Don't stop yet."

"We must bring Yanukovych and the scum that surrounds him to Maidan," she said, according to the BBC.

Her speech was briefly interrupted by a heckler but she later carried on addressing the crowd. Some people welcomed her speech but others whistled.

Saturday's appearance brought Tymoshenko back to the square where she attracted world attention in the 2004 Orange Revolution protests, a riveting figure then for her rhetoric, her elaborate blond peasant braid and her fashionable clothing.

After the protests forced the rerun of a presidential election nominally won by her foe Viktor Yanukovych, Tymoshenko became prime minister. But when Yanukovych won the 2010 election, Tymoshenko was arrested and put on trial for abuse of office, an action widely seen as political revenge.

Now Yanukovych once again appears on the wane and Tymoshenko on the rise. After Friday's agreement between the president and the opposition that reduced Yanukovych's powers, Yanukovych has gone to Kharkiv in his support base of eastern Ukraine, leaving the capital effectively in the control of the opposition.