A leaked memo from Thai police has revealed that 10 people with suspected links to ISIS entered Thailand in October with the intent to stage attacks on Russians in the country. In the internal police memo dated last month, that has since been published by various Thai media outlets, Thai police urged heightened security in "target areas that Russian authorities are concerned about," citing Russian intelligence that claimed 10 Syrians entered Thailand between Oct. 15 and Oct. 31, according to Time.

"The document is real. We received it from Special Branch," said a police officer who handles international crime matters, speaking on the condition of anonymity.

"The original communication was by word of mouth between Russian and Thai police. I don't know how the document leaked," added the officer.

The memo states that the suspects, whose identities are unknown, split up and headed for different parts of the country after entering Thailand, according to CNN.

Four traveled to the seaside city of Pattaya, 90 miles south of Bangkok; two to the tourist island of Phuket, 520 miles southwest of Bangkok; two remained in the capital; and the remaining two's location is unknown, said the memo.

Deputy Police Spokesman Songpol Wattanachai told reporters that Russia is the only foreign entity that has supplied Thailand with any information about a potential ISIS threat, adding that police had been unaware about the rumored militants' identities, whereabouts or possible targets, according to Reuters.

Russia has become a prime target for ISIS after the country launched an aggressive airstrike campaign at Syria's behest at the end of September. Hostilities between the two have risen ever since the militant group took responsibility for the bombing of a Russian plane flying over Egypt Oct. 31 that killed all 224 passengers on board.