The Ukrainian government will draw up a law banning churches affiliated with Russia under moves described by President Volodymyr Zelenskiy as necessary to prevent Moscow being able to "weaken Ukraine from within."
In a move condemned in Moscow, Ukraine's National Security and Defence Council told the government to draft the law following a series of raids on parishes that Kyiv says could be taking orders from Moscow as Russia wages war on Ukraine.
The security council, which groups top security, military and political figures, also ordered investigations into suspected "subversive activities of Russian special services in the religious environment of Ukraine" and called for sanctions against unspecified individuals.
Ukrainian media quoted sources as saying a pro-Russia former lawmaker and a senior cleric already faced "personal" sanctions, but the reports could not be confirmed independently.
The Security Service of Ukraine (SBU) also continued its raids on Friday, saying it searched at least five parishes belonging to a branch of the Ukrainian Orthodox Church which until May was subordinated to the Russian Orthodox Church.
It also served a notice of suspicion to a former diocese head for allegedly coordinating a pro-Moscow information campaign with the head of the Russian Orthodox Church.
"We have to create conditions where no actors dependent on the aggressor state (Russia) will have an opportunity to manipulate Ukrainians and weaken Ukraine from within," Zelenskiy said in his nightly address to the nation on Thursday.
"We will never allow anyone to build an empire inside the Ukrainian soul."
A spokesperson for the church, Metropolitan Kliment, said his organisation "has always acted within the framework of Ukrainian law".
"Therefore, the state of Ukraine does not have any legal grounds to put pressure on or repress our believers," he said.
Former Russian President Dmitry Medvedev described the authorities in Kyiv as "satanists" and "enemies of Christ and the Orthodox faith".
"This is how the whole Christian world should treat them," he wrote on the Telegram messaging app.
Orthodox Christians make up the majority of Ukraine's 43 million people. Since the collapse of Soviet rule, competition has been fierce between the Moscow-linked church and an independent Ukrainian church proclaimed soon after independence.
A July survey by the Kyiv International Institute of Sociology of found that only 4% of Ukrainians affiliated themselves with the Moscow-subordinated church.
The branch has condemned Russia's invasion of Ukraine but many Ukrainians fear it could be a source of Russian influence. The Orthodox Church in Russia has backed the invasion.
Zelenskiy also said officials would look into whether the formerly Moscow-linked branch of the church was entitled to operate at the sprawling Pechersk Lavra monastery in Kyiv.