Thai police have received a warning from Russia's state security agency that 10 Syrians who may be linked to the Islamic State group could stage attacks in Thailand on targets associated with Russia and others opposed to the militants, officials said Friday.

National police deputy spokesman Col. Songpol Wattanachai confirmed the authenticity of a leaked police memo mentioning the intelligence warning. He told reporters that the information has not been verified.

The Islamic State group has claimed responsibility for bringing down a Russian jetliner over Egypt's Sinai region in October, describing it as retaliation for Russian airstrikes in Syria.

The Thai capital was the target of a bombing in August that killed 20 people, but it has been linked to militants from China's Muslim Uighur minority.

There have been few signs of IS activity in Thailand, though the group actively recruits volunteers from its Southeast Asian neighbors Malaysia and Indonesia — which are predominantly Muslim — to fight in Syria and Iraq.

The police memo, dated Nov. 17 and marked "urgent" and "confidential," cites Russia's Federal Security Service FSB warning that the 10 Syrians believed to be involved with IS entered Thailand in the second half of October. According to the memo, some of them went to Bangkok, Pattaya and Phuket.

Pattaya and Phuket are seaside resorts popular with foreign tourists, and Pattaya is especially popular with Russians.

"The objectives of these people are to cause harm to Russia's assets or those of its allies in Thailand," said the memo.

The police memo called on security officials to confirm the information and step up security at possible targets related to countries opposed to IS, specifically the United States, Britain, France, Germany, Sweden and Australia.

Police spokesman Songpol said that after October's deadly attacks in Paris, security had already been stepped up at venues in Bangkok such as embassies. He said the information was the first Thailand had received suggesting that IS-linked Syrians had entered the country.

Sidney Jones, an expert on Southeast Asian Islamist movements at the Jakarta-based Institute for Policy Analysis of Conflict, said that IS cells in Indonesia and other parts of Southeast Asia were getting more serious about establishing a more formal structure.