Ukraine has reached an agreement with pro-Russian separatists for a truce during the Christmas and New Year holidays that went into effect at midnight on December 22.
The United States is adding nearly three dozen people and companies to its sanctions list for activity directly or indirectly connected to the conflict in eastern Ukraine and the annexation of the Crimean Peninsula.
Russian President Vladimir Putin has said Moscow "will continue making efforts" to resolve trade disputes with the European Union and Ukraine.
Russia warned December 21 that any move by the European Union to cancel the Nord Stream gas pipeline from Russia's Baltic coast to Germany would only hurt Europe.
Ukrainian news media reported December 21 that the country's national security service has banned the leader of the U.S. rock band Limp Bizkit from entering the country for five years.
Last-ditch negotiations aimed at addressing Russia's concerns about a free trade agreement between the European Union and Ukraine ended without result December 21.
Russia's Finance Ministry says Ukraine has failed to repay a $3 billion Eurobond debt owed to Russia by December 21.
Russian news agencies have reported that a powerful explosive device went off late on December 21 in the city of Donetsk, in conflict-torn eastern Ukraine.
A Russian opposition activist who became the first person charged under a strict new protest law has reportedly fled to neighboring Ukraine, where he will seek political asylum.
President Vladimir Putin has said Russia is not trying to bring back the Soviet Union, but that "nobody wants to believe" it.
European Union ambassadors have agreed to extend economic sanctions against Russia for another six months over its role in the Ukraine conflict.
European Council President Donald Tusk says the proposed Nord Stream-2 pipeline extension does not meet EU energy rules on supply diversification and would undermine Ukraine's role as a gas transit state.