On 1 April, Russia took up the presidency of the 15-nation UN Security Council. Ukraine's foreign minister described the situation as "the worst joke ever for April Fool's Day".
Each of the council's 15 members takes up the presidency for one month. The last time Russia was in charge was in February 2022, the start of the invasion of Ukraine.
The Security Council is responsible for maintaining peace worldwide.
Ukrainian Foreign Minister Dmytro Kuleba said the move, which the UN described as inevitable since Russia is a permanent council member, was further proof that the international security aparatus is fatally flawed.
Noting that Russian President Vladimir Putin is wanted by the International Criminal Court on suspicion of having committed war crimes in Ukraine, a presidential spokesman in Kyiv said allowing Russia take control of the Security Council was "another rape of international law."
Russia promises 'new world order'
He went on to assert that a country that "wages an aggressive war, violates the norms of humanitarian and criminal law, destroys the UN Charter, neglects nuclear safety, can't head the world's key security body".
Moscow's ambassador to the UN, Vasily Nebenzya, told the Russian news agency Tass that he intends to oversee several debates, including one on arms control.
He said he hoped to discuss a "new world order" which would end global domination by the United States.
Ukrainian President Volodymyr Zelensky has called for Russia to be removed from the Security Council, or for the body to be dissolved. The UN charter does not allow for the removal of a permanent member.
Russia is one of five nations, the others being France, UK, US and China, which can veto Security Council decisions.
Twice last year, Russia prevented the passage of resolutions calling for the end of the invasion of Ukraine and the restoration of sovereign territory occupied by Moscow's troops.