Posters showing a portrait of Turkish President Recep Tayyip Erdogan and reading “Wanted,” “Erdogan, Turkey,” are left after a protest at the Turkish Embassy in Moscow, Russia, Wednesday, Nov. 25, 2015.

Turkish President Tayyip Erdogan warned Russia on Friday not to “play with fire”, citing reports Turkish businessmen had been detained in Russia, while Moscow said it would suspend visa-free travel with Turkey.

Relations between the former Cold War antagonists are at their lowest in recent memory after Turkey shot down a Russian jet near the Syrian border on Tuesday. Russia has threatened economic retaliation, a response Erdogan has dismissed as emotional and indecorous.

The incident has proved a distraction for the West, which is looking to build support for the U.S.-led fight against ISIS in Syria. The nearly five-year-old Syrian civil war has been complicated by Russian air strikes in defense of President Bashar al-Assad.

Turkey, which has long sought Assad’s ouster, has extensive trade ties with Moscow, which could come under strain. Erdogan condemned reports that some Turkish businessmen had been detained for visa irregularities while attending a trade fair in Russia.

“It is playing with fire to go as far as mistreating our citizens who have gone to Russia,” Erdogan told supporters during a speech in Bayburt, in northeast Turkey. “We really attach a lot of importance to our relations with Russia … We don’t want these relations to suffer harm in any way.”

He said he may speak with Russian President Vladimir Putin at a climate summit in Paris next week. Putin has so far refused to contact Erdogan because Ankara does not want to apologize for the downing of the jet, a Putin aide said.

Erdogan has said Turkey deserves the apology because its air space was violated.

Russian Foreign Minister Sergei Lavrov said on Friday Moscow would suspend its visa-free regime with Turkey as of Jan. 1, which could affect Turkey’s tourism industry.

Turkey’s seaside resorts are among the most popular holiday destinations for Russians, who make up Turkey’s largest number of tourist arrivals after Germany.

An association of Russian defense factories, which includes the producers of Kalashnikov rifles, Armata tanks and Book missile systems, has recommended its members suspend buying materials from Turkey, according to a letter seen by Reuters. That could damage contracts worth hundreds of millions of dollars.

Russia’s agriculture ministry has already increased checks on food and agriculture imports from Turkey, in one of the first public moves to curb trade.

Turkish government spokesman Numan Kurtulmus said on Friday Turkey’s council of ministers was also discussing which measures to take, but that he hoped that these would not last long.

“I couldn’t imagine that Russia would completely abandon its relations with Turkey over such an incident,” he told a news conference. “For us it’s impossible for Turkey to abandon its relations with Russia over such an incident.”

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