Thousands of demonstrators were in the streets of Kyiv as Ukrainians on both sides of the European-integration debate try to send a message to coincide with the end of a two-day EU summit that dealt a blow to pro-Western forces in Ukraine.
Ukrainians have been camping out at Independence Square in the capital for much of the past week, since President Viktor Yanukovych and his political allies suspended advanced talks on a possible Association Agreement with Brussels.
An opposition resolution read out at the Kyiv rally demanded Yanukovych's resignation and vowed to continue "the fight for a European Ukraine."
Arseniy Yatsenyuk, leader of the Batkivshchyna faction in the national legislature, told the crowd that the parliamentary opposition will seek a bill to impeach Yanukovych.
Meanwhile counterdemonstrators, many of them reportedly bussed in from the more pro-Russian eastern part of the country, chanted Yanukovych's name and celebrated his about-face at a square just a few hundred meters away.
Riot police were keeping a close watch over events.
EU leaders at the close of the Third Eastern Partnership Summit in Vilnius, Lithuania, blamed Russia for scuttling the key deal between the bloc and Kyiv.
Moscow recently intensified its pressure on a number of Ukraine and other Eastern Partnership states -- which include Armenia, Azerbaijan, Belarus, and Georgia and Moldova, both of which initialed Association Agreements in Vilnius
-- to discourage their deeper ties with the European Union.
Ukrainian lawmakers last week failed to pass legislation that could have fulfilled one of EU officials' major demands on Kyiv -- to allow jailed former Prime Minister Yulia Tymoshenko to travel abroad for medical treatment -- and demonstrated Yanukovych and the ruling party's continued commitment to EU integration.
That snub and the subsequent call by Yanukovych for greater regard for Ukraine-Russia relations sparked demonstrations attended by tens of thousands of Ukrainians angered at the seeming volte-face.
In the Lithuanian capital on November 29, European Commission President Jose Manuel Barroso claimed the era of "limited sovereignty was over in Europe."
WATCH a live stream (in Ukrainian) from the pro-EU protest in central Kyiv by RFE/RL's Ukrainian Service:
German Chancellor Angela Merkel -- who told Yanukovych tersely in a face-to-face meeting
at the summit that "we expected more" -- remarked that "we should overcome the mentality 'either us or them.' The Cold War is over."
French President Francois Hollande said Ukraine was heavily pressured, "notably through gas," by Moscow not to sign association and free-trade accords with the EU.
After suggesting he would commit Ukraine to a deal at the summit, Yanukovych last week suddenly froze the long-negotiated Association Agreement and placed an emphasis on ties with neighboring Russia.
In the Lithuanian capital, Yanukovych said Kyiv wants to sign a pact "in the nearest future" despite not doing so during the summit.Barroso rejected Kyiv's suggestion that Moscow could participate in talks over preparing Ukraine economically for an Association Agreement.
"[W]e don't need a trilateral agreement for a bilateral deal," Barroso said. "When we make trade agreements with Canada or South Korea, we don't invite a third country to negotiate the finalization of this bilateral agreement."
A final summit declaration said all participants in the Vilnius summit "take note of the unprecedented public support for Ukraine's political association and economic integration with the EU."
The rallies in the Ukrainian capital have been the largest since the 2004 Orange Revolution that ousted Yanukovych after an electoral victory denounced as rigged. Much of the Orange Revolution played out nine years ago on the same Independence Square, "Maidan Nezalezhnosti," where these fresh protests are centered.
Based on reporting by AP, Reuters, AFP, and RFE/RL's Ukrainian Service