A 26-year-old Tajik national has been detained in St. Petersburg on a charge of justifying terrorism, the Investigative Committee said on March 28.
The arrest comes amid an ongoing crackdown on migrant laborers following a terrorist attack near Moscow last week that has left at least 143 people dead and hundreds wounded.
Investigators say the Tajik citizen, who was not named by authorities, posted comments justifying terrorism under a video taken from last week's attack on the Crocus City Hall entertainment center in the city of Krasnogorsk, near Moscow, that was claimed by the Islamic State extremist group.
In an online statement, the Investigative Committee posted a video that purportedly showed the detained man apologizing.
The independent Astra Telegram channel identified the man as Bahodur Zuhurov.
A court decision on the suspect's possible pretrial arrest is pending. If convicted, the man may face up to five years in prison.
Earlier, a spokeswoman for the St. Petersburg court, Darya Lebedeva, said another Tajik national, Ahmad Faizulokhonzoda, will be deported from Russia for violating registration regulations and for being a member of a Telegram chat group allegedly used to recruit the suspects who were arrested over the March 22 attack.
Faizulokhonzoda was ordered to pay a 5,000 ruble ($55) fine and placed in an immigration center.
Russian officials said earlier that 11 suspects, including four men who allegedly attacked the entertainment center, were detained. The four men, all ethnic Tajiks, on March 24 were sent to pretrial detention until at least May 22.
On March 25, three Tajik men residing in Russia and a Kyrgyzstan-born Russian citizen were sent to pretrial detention for at least two months.
Neighbors of one of the suspects arrested in Russia, Dalerjon Mirzoev, told RFE/RL on March 28 that his brother, Ravshanjon Mirzoev, had joined the Islamic state group in Syria in 2016.
RFE/RL correspondents found Ravshanjon Mirzoev's name on a list of people wanted in Tajikistan on unspecified charges. A source close to the Central Asian nation's law enforcement told RFE/RL that Ravshanjon Mirzoev died four years ago in the Middle East.
The Crocus City Hall attack sparked a wave of anti-migrant and xenophobic manifestations across Russia after authorities detained 11 suspects, eight of whom -- mostly ethnic Tajiks -- were sent to pretrial detention.
This week, a banner saying "Visa-Free Regime Kills" appeared at a makeshift memorial near what was left of the Crocus City Hall.
Russian lawmaker Mikhail Sheremet proposed restrictions on foreigners' visits to the country during the "special military operation" -- the official term for Russia's ongoing invasion of Ukraine.
Another lawmaker, former presidential candidate Vladislav Davankov, said migrant laborers should be placed under digital monitoring and should be deported after committing even minor violations.
Some comments under the Russian lawmakers' online statements call for the closure of all mosques in Russia and keeping migrant workers in special dwellings without the right to freely move about in the country.
Members of indigenous ethnic groups from Russia's ethnic republics have also faced harassment, aggression, and violence in public places in Moscow and other Russian cities in recent days.
Human rights defender Valentina Chupik told Current Time that during the week in just one court in Moscow's Cheryomushki district, police brought about 25 labor workers, mostly Tajiks, each hour for deportation.
"I have not slept for five nights. I receive about 1,000 complaints each day, of which some 700 are linked to migrants' detainments. In all, I have now 3,500 complaints from [migrant workers] detained by police. Some 150 complaints a day are about the beating of migrants by police," Chupik said.
Other complaints include migrants' statements accusing police officers of robbing them during questioning and falsely accusing them of disobeying police orders, she said.
According to Chupik, authorities intentionally incite anti-migrant sentiments "to distract people's attention" from the "fact that the terrorist attack was overlooked" after Russian authorities received warnings from the United States that an attack was imminent.
"The goal is to deflect people's anger from the authorities to a known weak group of people who can be easily subdued and is clearly 'alien,'" Chupik said.