Two American Mormons have been detained and found guilty of migration offences – adding to already fraught US-Russia relations.

A spokesman for the Russian Foreign Ministry on Wednesday evening confirmed two US citizens had been arrested in the port city of Novorossiysk, home to a major Russian navy base, but refrained from giving additional details.

According to the Kommersant newspaper, David Gaaga and Cole Brodovsky were arrested while addressing a local branch of the Church of Jesus Christ of Latter-day Saints (Mormons) in English. The men were usually based in Rostov-on-Don, 200 miles to the north, the paper added.

In a strict reading of Russia's migration laws, prosecutors contended that such "English lessons" were not compatible with the religious visas the men had used to enter the country with. In court, the men insisted that discussions in English were part of their religious work.

Unsurprisingly, a district judge agreed with prosecutors, finding them guilty of violating migration rules inside a border zone. According to the judgment, the men were fined 2,000 roubles (approx £25) each and moved to a temporary detention centre ahead of their likely deportation.

In pictures: US banker jailed by Russian court for fraud Show all 14 1 /14 In pictures: US banker jailed by Russian court for fraud In pictures: US banker jailed by Russian court for fraud 2019-02-15T185050Z-1041913715-RC11E657B970-RTRMADP-3-RUSSIA-BUSINESS-DETENTION.JPG Founder of the Baring Vostok private equity group Michael Calvey, who was detained on suspicion of fraud, reacts inside a defendants' cage as he attends a court hearing in Moscow, Russia February 15, 2019. REUTERS/Tatyana Makeyeva In pictures: US banker jailed by Russian court for fraud 07372543.jpg US investor Michael Calvey attends a hearing on investigators' motion on his arrest in connection with Baring Vostok criminal case at the Basmanny district court in Moscow, Russia, 15 February 2019. US investor Michael Calvey, senior partner at the Baring Vostok private equity funds, was detained in Moscow on fraud charges along with some other partners of the company. EPA/MAXIM SHIPENKOV In pictures: US banker jailed by Russian court for fraud 1125031857.jpg MOSCOW, RUSSIA - FEBRUARY 15, 2019: Alexei Kordichev, chairman of the Board of Directors at PNB Banka (previously Norvik Banka), former chairman of the Board at Vostochny Bank (Orient Express Bank), suspected of large-scale fraud, ahead of a hearing at Moscow's Basmanny District Court. The court considers arresting Kordichev in connection with the criminal case against Michael Calvey, founder of the Baring Vostok Investment Fund. Sergei Bobylev\\TASS via Getty Images In pictures: US banker jailed by Russian court for fraud 1125022312.jpg Baring Vostok Investment Manager Maxim Vladimirov suspected of complicity in a large-scale fraud attends a hearing at Moscow's Basmanny District Court to consider his arrest in connection with the criminal case against Michael Calvey, founder of the Baring Vostok Investment Fund. Sergei Bobylev\\TASS via Getty Images In pictures: US banker jailed by Russian court for fraud 1125022291.jpg MOSCOW, RUSSIA - FEBRUARY 15, 2019: Baring Vostok Partner Vagan Abgaryan suspected of complicity in a large-scale fraud attends a hearing at Moscow's Basmanny District Court to consider his arrest in connection with the criminal case against Michael Calvey, founder of the Baring Vostok Investment Fund. Sergei Bobylev\\TASS via Getty Images In pictures: US banker jailed by Russian court for fraud 07372494.jpg US investor Michael Calvey (back C) is escorted to attend hearing on investigators' motion on his arrest in connection with Baring Vostok criminal case at the Basmanny district court in Moscow, Russia, 15 February 2019. US investor Michael Calvey, senior partner at the Baring Vostok private equity funds, was detained in Moscow on fraud charges along with some other partners of the company. EPA/MAXIM SHIPENKOV In pictures: US banker jailed by Russian court for fraud urn-publicid-ap.org-93277d8c217f4568b96b8b1904b7e396.jpg Founder of the Baring Vostok investment fund Michael Calvey sits in a cage in the court room in Moscow, Russia, Friday, Feb. 15, 2019. A veteran U.S. investment fund manager has been detained in Moscow and faces fraud charges. A Moscow court said on Friday that Michael Calvey, founder and senior partner at Baring Vostok equity firm, was detained alongside two other fund managers. AP Photo/Alexander Zemlianichenko In pictures: US banker jailed by Russian court for fraud 07372493.jpg The Pervoye Kollektorskoye Bureau (First Collection Bureau) CEO Maxim Vladimirov is escorted to attend hearing on investigators' motion on his arrest in connection with Baring Vostok criminal case at the Basmanny district court in Moscow, Russia, 15 February 2019. U.S. investor Michael Calvey, senior partner at the Baring Vostok private equity funds, was detained in Moscow on fraud charges along with some other partners of the company, including business partner Maxim Vladimirov. EPA/MAXIM SHIPENKOV In pictures: US banker jailed by Russian court for fraud 1125031852.jpg Alexei Kordichev (C), chairman of the Board of Directors at PNB Banka (previously Norvik Banka), former chairman of the Board at Vostochny Bank (Orient Express Bank), suspected of large-scale fraud, ahead of a hearing at Moscow's Basmanny District Court. The court considers arresting Kordichev in connection with the criminal case against Michael Calvey, founder of the Baring Vostok Investment Fund. Sergei Bobylev/TASS In pictures: US banker jailed by Russian court for fraud 1125031860.jpg MOSCOW, RUSSIA - FEBRUARY 15, 2019: Michael Calvey, founder of the Baring Vostok Investment Fund, suspected of large-scale fraud, during a hearing at Moscow's Basmanny District Court. Sergei Bobylev\\TASS via Getty Images In pictures: US banker jailed by Russian court for fraud 1125032009.jpg Michael Calvey, founder of the Baring Vostok Investment Fund, suspected of large-scale fraud, during a hearing at Moscow's Basmanny District Court. Sergei Bobylev\\TASS via Getty Images In pictures: US banker jailed by Russian court for fraud 2019-02-15T152441Z-650771727-RC114BA8B5A0-RTRMADP-3-RUSSIA-BUSINESS-DETENTION.JPG Founder of the Baring Vostok private equity group Michael Calvey, who was detained on suspicion of fraud, stands inside a defendants' cage as he attends a court hearing in Moscow, Russia February 15, 2019. REUTERS/Tatyana Makeyeva In pictures: US banker jailed by Russian court for fraud AFP-1DH711.jpg US investor Michael Calvey, the head of investment company Baring Vostok, detained on fraud charges, attends a court hearing in Moscow's Basmanny Court on February 15, 2019. - Russia has detained the US head of a major investment firm on suspicion of fraud along with several other people from the fund and other businesses, a court spokesperson told Russian news agencies. VASILY MAXIMOV/AFP/Getty Images In pictures: US banker jailed by Russian court for fraud 1125062626.jpg US investor, founder and senior partner at Baring Vostok, Michael Calvey (back), who is suspected of involvement in swindling 2.5b roubles from Vostochny Bank, attends a hearing at Moscow's Basmanny District Court into an application for a warrant for his detention; 5 Baring Vostok workers, including Calvey, and one Norvik Banka worker, have been arrested in connection with the ongoing probe into the fraud; Baring Vostok holds a controlling stake in Vostochny Bank. Sergei Bobylev\\TASS via Getty Images

Mormon missionaries continue to practice legally in Russia, having escaped the provisions of new "anti-terror" laws applied to many other "foreign" minority religious groups. Last month, a group of Jehovah's Witnesses in the Siberian city of Surgut complained of harassment and torture at the hands of Russian law enforcement.

Friday's arrests also come on the back of the December arrest of US citizen Paul Whelan over alleged espionage attacks. He spent his 49th birthday in prison this week, with little prospect of an imminent release.