Former Ukrainian prime minister Yulia Tymoshenko appeared before crowds gathered at the protester in capital Kiev hours after being released from prison after two and a half years in captivity.
In an address Tymoshenko asked the protestors to keep occupying the square.
According to Fox News, her speech to the crowd of about 50,000 was the latest stunning development in the country's political crisis.
Only a day earlier, her rival, President Viktor Yanukovych, signed an agreement with protest leaders that cut his powers and called for early elections.
Yanukovych meanwhile appeared to be losing power by the hour.
Earlier in the day Tymoshenko promised to run for president, saying she will make it so that no drop of blood that was spilled will be forgotten.
Her release on Saturday was made possible by a European-brokered peace deal between Yanukovych, and the opposition.
The European Union condemned the jailing of Tymoshenko as political and urged Yanukovych to free her.
In the address, Tymoshenko called the protestors her heroes and the best thing in Ukraine!
She urged the demonstrators not to yield from their encampment in the square, known in Ukrainian as the Maidan.(ANI)