Ukraine on Tuesday accused Russia of the assassination of "perceived opponents" in a case lodged at the European Court of Human Rights.
The case, filed last week, claims Russia carried out "state-authorised assassinations in Russia and on the territory of other states ... outside a situation of armed conflict", the court said.
Europeiska Pravda, a Ukrainian news outlet specialising in European affairs, said the complaint included the case of leading Kremlin critic Alexei Navalny, who was poisoned last year with the Novichok nerve agent in an attack blamed on Moscow.
This was not confirmed immediately by the Strasbourg court, which provided no details of any of the alleged assassinations in its statement.
It is the ninth case filed by Ukraine against Russia at the court, which hears complaints over alleged breaches of the European Convention on Human Rights.
"We have finally done this," Ukrainian deputy justice minister Ivan Lishchyna said. "We tried to cover all cases for which there is solid evidence of Russian involvement."
Ukraine also accuses Russia of failing to investigate the assassinations and "deliberately mounting cover-up operations aimed at frustrating efforts to find the persons responsible", the court said.
Ukraine argues that such failures constitute an infringement of the right to life, which is protected by the Convention on Human Rights, to which Russia is a signatory.
Other cases filed by Ukraine relate to the downing of Malaysia Airlines Flight MH17 over eastern Ukraine in July 2014, human rights breaches in the Crimean Peninsula that Moscow annexed from Ukraine in 2014, and Russia's seizure of three Ukrainian navy vessels in the Kerch Strait in 2018.
Ukraine's government has been at war with separatists in eastern Ukraine since pro-Russian militias launched a bid for independence after the annexation of Crimea.
Nearly 13,000 people have been killed in the conflict, which deepened Russia's estrangement from the West.