Russia says the International Court of Justice (ICJ) in The Hague has no jurisdiction to issue an order Ukraine seeks to halt Moscow's support for separatists in eastern Ukraine and Crimea.
The matter is "clearly outside the court’s competence," Russian Foreign Ministry Legal Department Director Roman Kolodkin told the court on March 7, a day after lawyers for Ukraine accused Russia of making it "impossible for Ukrainian citizens to feel safe anywhere in their country."
Judges at the ICJ, the United Nations highest judicial body, hear disputes between states. Cases can take years to pass through the court and although its rulings are final and binding, it has no means of enforcing decisions.
Moscow seized control of Ukraine's Crimean Peninsula in March 2014 and has supported separatists in eastern Ukraine in fighting that has since killed more than 9,750 people.
Kyiv has accused Russia of violating UN conventions against terrorism and discrimination by supporting groups in eastern Ukraine and Crimea.
It also accuses Russia of mistreating Crimea's Tatar and ethnic Ukrainian populations since it seized control of the peninsula.
The Kremlin has denied sending troops or military equipment to eastern Ukraine despite what Kyiv and Western countries say is incontrovertible evidence to the contrary.
The United States and other Western powers have placed economic sanctions on Moscow because of its interference in Ukraine.
Kolodkin said on March 7 that allegations Russia participated in the armed conflict in eastern Ukraine are groundless.
"The Russian Federation complies fully with its obligations under [the] treaties that are now relied upon by Ukraine,” he also told the court.
"Ukraine has not provided substantiations for its position that there are circumstances falling under the convention" on eliminating discrimination, the Russian Foreign Ministry said.
The first round of hearings is expected run until March 9 and will largely consist of procedural matters.
Georgia brought a similar case against Russia, but the court ruled in 2011 that it had no jurisdiction to rule on the matter.
With reporting by AP, Reuters, Interfax, and TASS