Ukrainian President Viktor Yanukovych has condemned what he calls "actions" that have led to violence during opposition demonstrations in Kyiv.
The Ukrainian president said Saturday he was "deeply outraged" by the violence at the capital's Independence Square, without directly blaming police.
Riot police in Ukraine used batons and stun grenades to break up an opposition demonstration early Saturday, after the president failed to sign a free trade pact with the European Union. Numerous injuries were reported.
He called for an immediate investigation in order to punish those responsible.
The U.S. State Department also condemned the attack against the demonstrators, saying "violence and intimidation should have no place in today's Ukraine."
The rights group Amnesty International called the violence a "shameful disregard for peoples' rights." It called for an independent investigation into the allegations.
On Friday, the European Union criticized Russia for pressuring Ukraine into abandoning the landmark free trade deal with the European bloc.
The snub, announced last week by Mr. Yanukovych, reverberated through an EU summit in the Lithuanian capital, Vilnius, where German Chancellor Angela Merkel was captured Friday on video telling the Ukrainian leader, "We expected more."
Mr. Yanukovych responded, telling the German leader, "The economic situation in Ukraine is very hard. And we have big difficulties with Moscow."
The summit, which ended Friday, had been expected to showcase the signing of the agreement.
As last-minute negotiations failed, thousands of opposition protesters in Kyiv gathered for a second time this week in the center of the city to demand the president's resignation.
European news reports say the EU-Ukraine deal began unraveling in late October, when Moscow demanded that cash-strapped Kyiv immediately make full payment of a nearly $1 billion natural gas bill, or face a gas cutoff as winter braces the region.
Moscow has also in recent months imposed restrictions on Ukrainian imports, dragging the Ukrainian economy into recession and triggering a warning from Moscow of more economic difficulties if Kyiv signed the EU pact.
Last week, as the Ukrainian president scuttled the EU deal, Ukrainian Prime Minister Mykola Azarov said the country's top priority now is to repair relations with Moscow.