Those responsible for the violence on Independence Square in Kyiv on November 30 must be brought to justice, and the detainees must be released, U.S. Assistance Secretary of State Victoria Nuland has said.

"Violence, or the threat of violence, is impermissible in a democratic state. Those responsible for the violence on November 30 must be brought to justice, and detainees must be released," the U.S. Embassy in Ukraine quoted her as saying in her opening remarks at a press conference in Tbilisi on Friday.

Nuland also said that six days had gone by with no accountability.

"Again, the voices of the Ukrainian people must be heard. They are calling for a European future: that's a free and democratic future; judicial accountability; human dignity and the restoration of Ukraine's economic health," she said.