Thai police officers stand guard outside French Embassy in Bangkok, Thailand.

Ten Syrians “related to” ISIS entered Thailand in October to attack Russian interests, Thai police said in a leaked document citing information from the Russian Federal Security Service.

In the document, Special Branch police urged an intensification of security around “target areas that Russian authorities are concerned about” including venues associated with allies that have taken part in attacks on ISIS in Syria.

Russia began air strikes in Syria on Sept. 30 and has stepped up attacks in recent weeks. An ISIS affiliate claimed responsibility for downing a Russian airliner over Egypt in October, killing all 224 people on board.

Thailand’s Special Branch, which deals with national security issues, circulated the document to other police units, two senior police officers told Reuters.

Marked “Urgent” and dated Nov. 27, the Special Branch police said intelligence from Russia warned that the 10 Syrians entered Thailand between Oct. 15 and Oct. 31. The document was circulating on social media on Thursday.

“The document is real. We received it from Special Branch,” said one of the police officers, who handles international crime matters. He declined to be identified because of the sensitivity of the matter.

“I have to deal with this issue now,” he said. “The original communication was by word of mouth between Russian and Thai police. I don’t know how the document leaked.”

The Special Branch, which sent the document to investigative divisions within the national police, said four of the suspects travelled to the seaside city of Pattaya, two to the tourist island of Phuket, two to Bangkok and two to an unknown destination.

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