Tens of thousands of pro-Western Ukrainians have massed in Kyiv to protest the beating in a clash between protesters and police of prominent opposition leader Yuriy Lutsenko.
The rally comes after the 49-year-old former government cabinet member under jailed ex-premier Yulia Tymoshenko was transferred out of intensive care late on January 11. His wife said he was in "moderate" condition.
Lutsenko was beaten along with other demonstrators overnight on January 10-11.
The Friday-night protest was against a Kyiv court's sentencing three men to six years in jail for allegedly plotting to blow up a statue of Lenin in 2011.
A Lenin statue in the capital was torn down by pro-EU protesters in early December, and several statues of the communist revolutionary have been vandalized since then.
Opposition leader Vitali Klitschko told the crowd at the January 12 rally that police violence against protesters showed the importance of a continued effort to topple the administration of Ukrainian President Viktor Yanukovych.
The so-called Euromaidan protests were sparked by Yanukovych and his political allies' decision in November to ditch an association and trade deal with the European Union in favor of tighter ties with Russia.
"Today the authorities use the police as a weapon, silencing the people's mouths with batons," Klitschko said. "We don't want to live under such conditions. We will not live like that and we will fight to change the country. I am certain that this split [between the public and the police] also needs to be eliminated. Law must prevail."
Klitschko, addressing cheering supporters from a makeshift stage, said the opposition would organize a national strike -- "first a short one, as a warning, and then a full-scale one that lasts a long time."
Fellow opposition lawmaker Arseniy Yatsenyuk announced that he would be sending an envoy to a U.S. Senate hearing set for January 15 during which he will press Washington to impose economic sanctions against members of the government.
"We have a key request to our Western partners -- it is time to act. The time for talks is over," Yatsenyuk said. "The first to be sanctioned by the West is supposed to be [Ukrainian] Interior Minister [Vitaliy] Zakharchenko and their entire gang that gave orders to beat people. This is our message to the West."
Speakers at the rally also urged the European Court of Human Rights in Strasbourg to expedite its hearing of a challenge to the jailing of Tymoshenko, RFE/RL's Ukrainian Service reported
Chants of "Yulia! Freedom!" were heard at the January 12 demonstration on Independence Square -- the hub of six weeks of the antigovernment protests.
Tymoshenko's case has been characterized as politically motivated among EU leaders and by rights defenders in Ukraine and abroad.
Her case had ratcheted up tensions between Kyiv and Brussels in the run-up to Yanukovych's decision to suspend work on the EU Association Agreement.
Based on reporting by AFP, AP, and RFE/RL's Ukrainian Service