Russia on Saturday demanded the immediate release of a senior Orthodox cleric detained in Kyiv on suspicion of inflaming religious hatred and justifying Russia's invasion of Ukraine.

A Kyiv court ordered pre-trial detention on Friday for Metropolitan Pavlo, a senior figure in the Ukrainian Orthodox Church who had been under house arrest since April.

"We demand strict compliance by the Kyiv regime with its international legal obligations, the immediate release of Metropolitan Pavlo, who is suffering from a serious illness, and the provision of proper medical care for him," Russian Foreign Ministry spokeswoman Maria Zakharova said. 

She called it "yet another manifestation of political arbitrariness and lawlessness," linking the case to Ukraine's moves to evict Orthodox monks from a renowned monastery in Kyiv.

Ukraine has been cracking down on the Moscow-linked Ukrainian Orthodox Church, claiming it is pro-Russian and collaborating with Moscow. The church denies that and says it cut all ties with Moscow last year, but many of its churches have been searched and dozens of clergy have faced charges.

On Thursday, Ukraine's SBU security service said it advised Pavlo of new allegations in connection with a media interview he gave in which he is alleged to have denied the existence of Ukraine as a sovereign state.

Patriarch Kirill, head of the Russian Orthodox Church, on Saturday appealed to Pope Francis, the head of the United Nations and other religious and political figures to show support for the detained cleric.

"I urge you to pay attention to the ongoing persecution of the canonical Ukrainian Orthodox Church in Ukraine and to take all possible measures to protect Metropolitan Pavlo ... from lawless persecution," Kirill said.