"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 in a statement.
Pillay's office said the political crisis in Ukraine "took a violent turn for the worse" Tuesday when protesters marched on government buildings in Kiev. At least 22 people were killed during clashes in the capital city between police and protesters.
The U.S. and British governments issued travel warnings Tuesday for Ukraine. The U.S. State Department said the "situation in Ukraine is unpredictable."
Demonstrations broke out in November when the Ukrainian government suspended efforts to sign free trade and association agreements with the European Union in order to protect its economic ties with Russia.
European Commission President Jose Manuel Barroso said Wednesday there's no excuse for the level of violence in Ukraine.
"We call on all sides to immediately put an end to the violence and engage into a meaningful dialogue, responding to the democratic aspirations of the Ukrainian people," he said in a statement.