Europe's top rights court on Tuesday condemned Russia for deliberately tolerating systemic rights violations in the Ukrainian Black Sea peninsula of Crimea since its 2014 annexation.

The ECHR's grand chamber, the court's highest instance, concluded "that the incidents had been sufficiently numerous and interconnected to amount to a pattern or system of violations".

"The apparent lack of an effective investigation... proved that such practices had been officially tolerated by the Russian authorities," it added.

The court noted in particular violations of the European Convention on Human Rights due to the ill-treatment of Ukrainian soldiers, persons of Ukrainian ethnic origin, journalists and members of the Turkic Crimean Tatar minority.

The ECHR said such people had been secretly detained in Russian prisons outside Crimea and urged their safe return.

In Kyiv, the Ukrainian foreign ministry said it welcomed the ruling as a "milestone" judgement.

"The international judicial body has held Russia accountable for systematic and widespread human rights abuses in Crimea.

"It is a crucial milestone on our path to ensuring international legal accountability for Russia."

Russia was expelled from the pan-European rights body the Council of Europe, of which the ECHR is part, following the start of its full-scale invasion of Ukraine in February 2022.

But complaints concerning violations allegedly committed by Russia before its September 16, 2022 exclusion from the body remain admissible at the court.

Ukraine has four other inter-state cases pending at the court against Russia, including motions concerning the invasion of February 2022 and the downing of Malaysia Airlines flight MH17 in 2014, a case brought jointly with the Netherlands.

Russia is also the subject of 7,400 individual applications to the ECHR concerning events in Crimea and the eastern Ukrainian region of Donbas, which is partially occupied by Russia.