UN human rights chief Navi Pillay has called for calm in Ukraine and demanded an independent investigation into deadly clashes between police and protesters.
"I strongly condemn the killings and urge the government and protesters to act to defuse tensions and to take swift action to find a peaceful solution," said Pillay, the UN high commissioner for human rights.
"I also call for an urgent and independent investigation to establish facts and responsibilities, including the possible use of excessive force, and to ensure accountability for these deadly clashes," she said in an official statement.
Ukrainian authorities said at least 25 people died in clashes between protesters and police that began on Tuesday in the main protest square in the Ukrainian capital Kiev.
The clashes mark the worst violence in the three-month-old standoff between Ukrainian President Viktor Yanukovych and anti-government protesters.
"I reiterate my call for the right to peaceful assembly, as provided under international human rights law, to be respected," said Pillay.
"Ukraine needs a dialogue between these opposing voices that respects the country's legal obligations, political commitments based on international human rights standards, and the recommendations made by the international human rights system," she said.
