Russia's President Vladmir Putin has signed a package of new anti-terrorism measures into law amid protests that they will be used to crack down on religious freedom. 

Among Christians in Russia, Protestant leaders are particularly fearful as the legislation – dubbed the Yarovaya law after one of its two sponsors, United Russia deputy Irina Yarovaya – targets unregistered congregations and house groups. 

According to Forum 18, which monitors religious freedom in Russia and former Soviet republics, the amendments to the Religion Law restrict those who can share beliefs to people with permission from members of state-registered religious groups and organisations.

This excludes people from "underground" churches which have chosen to operate without state permission. They also prohibit even the informal sharing of beliefs, for example responding to questions or comments.

The amendments also restrict the beliefs that can be shared and specify a restricted list of places where beliefs may be shared. They ban any beliefs from being shared in residential buildings, and bar the conversion of residential property to religious use. There are heavy financial penalties for breaching the law.

The new laws, which come into effect on July 20, represent the culmination of attempts by anti-religion campaigners to limit religious expression. Previous attempts by politicians to introduce bills on missionary activity were not supported by the government, according to Forum 18, but the restrictions were added at the last minute to the anti-terrorism legislation. Human Rights Watch has documented its chaotic passage, which included the last-minute withdrawal of a proposal to remove Russian citizenship from anyone who "worked for an international organisation" in whose creation Russia did not take part.

The new laws have drawn fierce protests from within Russia and abroad. Forum 18 cites lawyer Vladimir Ryakhovsky of the Slavic Centre for Law and Justice, who wrote on Facebook when President Putin signed the bill into law: "Today is indeed a black day on the calendar. Hope was that Vladimir Putin would not in the end sign this law. A law which openly contradicts the gospel command 'go and make disciples' and, in addition, violates the constitutional rights of citizens." He said that the amendments been drafted by "people who were absolutely not professionals and who didn't understand religious practice".

However, he indicated that the law would be challenged in Russia's Constitutional Court. Until then, he said: "Let's work out how to get round it, and then we'll seek to get it amended. Don't succumb to panic when they threaten you with all kinds of horror stories."

Deputy Bishop Konstantin Bendas of the Pentecostal Union said he hoped that deputies in the Duma to be elected in September will amend the law. He highlighted the need to change the provisions on "missionary activity" and the use of homes for meetings for worship.

A spokeswoman for the Council of Churches-Baptists told Forum 18: "We are distressed by the Law and see it as repressive for believers in our country, because the Law contradicts the Bible." She added that "we must assume there will be repression and persecution".

The new laws have also drawn international protests. The United States Commission on International Religious Freedom (USCIRF) said they would grant authorities "sweeping powers to curtail civil liberties, including setting broad restrictions on religious practices that would make it very difficult for religious groups to operate".

USCIRF chair Thomas Reese said: "These deeply flawed anti-terrorism measures will buttress the Russian government's war against human rights and religious freedom.

"They will make it easier for Russian authorities to repress religious communities, stifle peaceful dissent, and detain and imprison people. Neither these measures nor the currently existing anti-extremism law meet international human rights and religious freedom standards."

According to the Gospel Coalition, "The new law will impede the spread of the gospel and threatens to curtail the expression of our Christian brothers and sisters in that country. For this reason alone we should strongly oppose the totalitarian policy."