Thousands of people have gathered in the Ukrainian capital to protest against the president’s decision not to sign an agreement to increase ties with the EU. This was the first major opposition rally of the new year.
More than 10,000 people are reported to have turned out for Sunday's demonstration in Kyiv, as protests against the president's decision stretched into a seventh week.
Former heavyweight boxing champion Vitali Klitschko used a speech to the crowd to renew a call for the European Union to impose sanctions on Ukraine's leadership.
"Moral support for opponents of the government is not enough," Klitschko said, before encouraging the protesters to keep up the fight.
"The authorities are pretending they cannot hear us. I know it's hard for us, but we have enough strength to win," said Klitschko, the leader of the opposition Udar (punch) party, who announced last month that he was hanging up the boxing gloves to concentrate on politics full time.
Klitschko said he expected even more people to turn out in a fresh wave of protests to begin after the Orthodox Christmas holidays on Monday and Tuesday.
He also announced plans for a general strike, which he said would be "first a strike warning and then a real one if the authorities don't want to listen to us."
Another opposition leader, Arseniy Yatsenyuk, also offered encouragement to demonstrators manning the protest camp on the Maidan, or Independence Square, which they have sealed off with improvised barricades.
"This year will be a very difficult one for us. We must hold onto the Maidan," Yatsenyuk said.
The protests were sparked by a decision by Ukrainian President Viktor Yanukovych not to sign an Association Agreement with the European Union, a u-turn widely seen as having come as a result of pressure from Russia.
The demonstrations gained more steam after a police crackdown on one of the early protests.
Shortly after Yanukovych balked at signing the deal with the EU, Russian President Vladimir Putin offered Ukraine a $15-billion (11-billion-euro) loans package and cut the price the country has to pay for Russian gas imports.
pfd/msh (AFP, dpa)