Ukraine filed a lawsuit at the United Nations' highest court demanding that Russia immediately halt its support for pro-Moscow separatists fighting in eastern Ukraine.
The Ukrainian Foreign Ministry accused Russia of "acts of terrorism and discrimination in the course of its unlawful aggression" in the filing to the International Court of Justice, according to a ministry statement issued on Monday evening.
Russia has repeatedly denied sending troops or military equipment to eastern Ukraine. In Moscow, its foreign ministry said Russia would use all available means of legal defence against the suit.
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The filing itself has no direct consequences, though a finding by the court in Ukraine's favour could be enforceable in some national courts, theoretically triggering legal steps to freeze or seize Russian assets.
The Hague-based court had no immediate comment.
Kiev is also challenging Moscow's actions on its territory at the International Criminal Court and the European Court of Human Rights, while Ukrainian energy firms Ukrnafta and Stabil have asked the U.N.'s Permanent Court of Arbitration to compensate them for investments lost when Russia seized the Crimean peninsula.
Russia's foreign ministry said it had studied Ukraine's claims but that Kiev had not shown interest in dialogue with Moscow.
It added that it had sought answers from Ukraine about how the rights of ethnic Russians and Russian speakers in Ukraine were observed but that Ukraine had declined to discuss the issue in detail.
Russia annexed Crimea in March 2014, and fighting broke out in eastern Ukraine the following month between pro-Russian rebels and Ukrainian government forces, a conflict in which close to 10,000 people have been killed.
In Monday's filing, Ukraine accused Russia of violating the Terrorism Financing Convention "by supplying weapons and other forms of assistance to illegal armed groups operating on Ukrainian territory".
Among the separatists' alleged crimes, the filing cited the downing of Malaysian Airlines Flight MH17 in 2014, the bombardment of residential areas in Mariupol and Kramatorsk, and the destruction of a civilian passenger bus near Volnovakha.