(CNN) Human rights groups and religious freedom advocates are blasting a Russian court for sentencing a Danish Jehovah's Witness to six years in a penal colony, saying the charges of "religious extremism" are unwarranted and unjust.

On Wednesday, Dennis Christensen was found guilty of violating a Russian law banning "the organization of a public or religious association ... or prohibition of activities in connection with extremist activities," according to TASS, Russia's state-run news agency.

A district court in Oryol, in western Russia, sentenced Christensen to six years in a penal colony, according to TASS. Christensen's attorney says he will appeal the ruling.

Christensen's sentencing is part of a campaign against Jehovah's Witnesses and other minority religions, religious freedom advocates say, as Russian Orthodox Christians seek to maintain their cultural dominance.

In 2017, Russia's Supreme Court banned Jehovah's Witnesses as an "extremist organization." According to a spokesman for the religion, 120 Jehovah's Witnesses are facing criminal charges in Russia, with 24 in pretrial detention and 28 under house arrest.

United Nations High Commissioner for Human Rights Michelle Bachelet said she is "deeply concerned" by Christensen's sentencing.

"The harsh sentence imposed on Christensen creates a dangerous precedent, and effectively criminalizes the right to freedom of religion or belief for Jehovah's Witnesses in Russia," Bachelet said.

Religious freedom advocates in the United States also expressed concern.

"Dennis Christensen's conviction represents the continued deterioration of religious freedom in (President Vladimir) Putin's Russia," said Kristina Arriaga, vice chair of the US Commission on International Religious Freedom

"Evidently, it's not enough for the state to brand peaceful groups like the Jehovah's Witnesses 'extremist'; it must also imprison their members."

Last year, the commission called for Russia be designated a "country of particular concern" under the International Religious Freedom Act. The US State Department has also placed Russia on a watch list for "engaging in or tolerating severe violations of religious freedom."

According to a US Commission on International Freedom report , the Russian government has "continued to target 'nontraditional' religious minorities, including Jehovah's Witnesses and Scientologists, with fines, detentions, and criminal charges under the pretext of combating extremism. Most notably, the Jehovah's Witnesses were banned outright, as was their translation of the Bible, and their followers persecuted nationwide."

Putin sent mixed messages about the persecution of Jehovah's Witnesses during a press conference in December. Asked why his government was going after a peaceful group, Putin dismissed such as a characterization as "complete nonsense."

But he added, "We should not forget that our society does not consist solely of religious sects. Ninety percent of citizens of the Russian Federation or so consider themselves Orthodox Christians. ... We should treat representatives of all religions in the same way -- this is true, but still, it is also necessary to take into account the country and the society in which we live."

In a statement, the European Union strongly condemned Christensen's conviction.

"The European Union expects Mr. Christensen to be released immediately and unconditionally. Jehovah's Witnesses, as with all other religious groups, must be able to peacefully enjoy freedom of assembly without interference, as guaranteed by the Constitution of the Russian Federation, as well as by Russia's international commitments and international human rights standards."

Before the ban, there were about 170,000 Jehovah's Witnesses in Russia, according to group. Known for their door-to-door evangelizing and refusal to serve in the military, Jehovah's Witnesses were founded in the United States in the late 19th century.

Christensen's group was "recognized as extremist" in 2016, according to TASS . A year later, he was detained and has been imprisoned for 622 days since, a Jehovah's Witness spokesman said.

"The regional prosecutor's office clarified that the convict knew that Jehovah's Witnesses were prohibited, but he continued to hold meetings and distribute books and brochures," TASS reported.

"Jehovah's Witnesses have a well-established international reputation for being peaceful, law-abiding citizen," said Paul Gillies, a spokesman for Jehovah's Witnesses.

"It is our hope that the Russian authorities will take this opportunity to correct the unjust decision to ban our activities, which has caused the imprisonment of our fellow believers."

Danish Foreign Minister Anders Samuelsen said on Twitter that he is "deeply concerned by sentencing of Dennis Christensen."

"Again call on #Russia to respect freedom of religion. Danish MFA will continue to follow closely and assist Dennis Christensen should he decide to appeal," Samuelsen said, referring to Denmark's Ministry of Foreign Affairs.

Deeply concerned by sentencing of Dennis Christensen. Again call on #Russia to respect freedom of religion. Danish MFA will continue to follow closely and assist Dennis Christensen should he decide to appeal #dkpol — Anders Samuelsen (@anderssamuelsen) February 6, 2019