Ukrainian protesters have mounted fresh protests in the capital, Kyiv. In a message to the crowd relayed by her daughter, imprisoned ex-premier Yulia Tymoshenko demanded the president's resignation.
At least 100,000 people were reported to have gathered in Kyiv on Sunday for renewed demonstrations against President Viktor Yanukovych.
The opposition supporters filled the city's independence square, also known as Maidan, where some protesters have set up a tent city. Members of the crowd waved European Union and Ukrainian flags, as well as the red-and-black banner of the anti-communist wartime Ukrainian Insurgent Army.
Yevgenia Tymoshenko, the daughter of jailed ex-Prime Minister Yulia Tymoshenko, delivered a message from her mother in prison, calling for Yanukovych's "immediate" resignation.
"Yanukovych took a decision to join the club of dictators," Yevgenia Tymoshenko quoted her mother as saying. "We must peacefully and legally oust him from power."
"He is no longer the president of our state, he is a tyrant who must answer for every drop of blood that has been shed," she added.
The decision of Yanukovych to abandon planned political and free trade agreements with the European Union have prompted a wave of protests from government opponents. The president on Friday further angered the opposition when he discussed the signing of a strategic partnership treaty with Moscow. Russian Prime Minister Vladimir Putin is eager for Ukraine to join a Customs Union that some Ukrainians complain would be the first step to a rebuilding of a new Soviet Union.
Organizers of the protest said they hoped to attract a million people.
"More than a million people have to make it clear to President Viktor Yanukovych that our demands must be met," said world boxing champion Vitaly Klitschko, leader of the opposition Udar (Punch) party, on Saturday night.
"Anyone who doesn't want to live in a police state, but in a modern country, cannot be indifferent," said Klitschko.
Tymoshenko's Fatherland party made an appeal via Twitter supporters to attend. "Go to the Maidan!" read its message. "We will chase him (Yanukovych) until he falls."
The AFP news agency reported that some 200,000 people had gathered by midday on Sunday.
Hundreds of thousands took to the streets last Sunday in what were the largest demonstrations since the pro-democracy Orange Revolution in 2004, which led to a rerun of elections that were initially claimed by Yanukovych. The rally saw unprecedented clashes between protesters and riot police, in which hundreds were injured.
Activists subsequently took control of Independence Square, keeping police out by erecting barricades.
Yanukovych, who faces an election in 2015, has promised a full investigation into the use of force by police, but has said he is not prepared to engage in talks with the opposition.
rc/pfd (AFP, AP)