Sweeping new anti-terrorism laws in Russia will stop Christians preaching, teaching, or sharing their faith, charities have warned.

Release International, which supports persecuted Christians around the world, has condemned the new legislation, agreed this month, for imposing severe restrictions on what Christians can say about their faith to their friends.

“The impact it’s going to have on Christians is really quite extraordinary, and very draconian,” a spokesman for Release International, Andrew Boyd, told Vatican Radio. The law is supposed to target terrorism and extremists, but sweeps up ordinary believers none the less, he said.

The charity’s chief executive, Paul Robinson, said: “This law limits where Christians can meet, and how they can tell others about their faith. Church leaders are warning of a return to the bad old Soviet era when the Church was driven underground.”

An open letter, signed by, among others, the head of the Protestant Churches of Russia, Sergei Ryakhovsky, said that the harsh new restrictions were taking Russia back to its “shameful past” under Soviet rule.

“The obligation on every believer to have a special permit to spread his or her beliefs, as well as hand out religious literature and material outside of places of worship and used structures, is not only absurd and offensive, but also creates the basis for mass persecution of believers for violating these provisions.

“[It’s] the most draconian anti-religion Bill to be proposed in Russia since Nikita Khrushchev promised to eliminate Christianity in the Soviet Union.”

Since the fall of communism the Russian Orthodox Church has prospered and a 1997 law established it as one of the country’s “traditional” faiths. It is often seen as close to the Putin regime and has sometimes endorsed the government’s increasingly nationalistic rhetoric in recent years.

But smaller Christian groups, often Protestant and Evangelical, and other sects including the Mormons and Jehovah’s Witnesses have long been viewed with suspicion and hostility by the Russian authorities. It is these more mission-focused Churches that are expected to bear the brunt of the new legislation’s restrictions.

The freedom-of-religion and human-rights advocacy group Forum 18 has also expressed concerns about the new law, which came into force on Wednesday, Church Times reported.

The group reported this month, after the law was signed, that Church leaders in Russia believed that Christians could not in good conscience abide by the new restrictions.

Deputy Bishop Konstantin Bendas, of the Pentecostal Union, told Forum 18 that there are sections of the law “which a good Christian cannot fulfil”.

A spokeswoman for the Baptist Council of Churches in Russia said: “We are distressed by the law, and see it as repressive for believers in our country, because the law contradicts the Bible. We must assume there will be repression and persecution.”

Missionaries and house churches have essentially become banned overnight, with individuals liable for fines of 50,000 roubles (about £600), and organisations facing fines of £1 million roubles (about £12,000).

Thomas Reese, who leads the United States Commission on International Religious Freedom, said that the legislation “will make it easier for Russian authorities to repress religious communities, stifle peaceful dissent, and detain and imprison people”.

Mr Robinson, whose organisation was founded during the Cold War to advocate for Christians suffering under Communism, urged British believers to pray for the Russian Church.

And to President Putin he had this message: “Please don’t confuse Christians with terrorists. Think again, sir, about this law, and its consequences for ordinary Russian believers.”