Bangkok: Islamic State is believed to have deployed 10 terrorists plotting attacks across Thailand, including at two tourist centres popular with Australians, according to Thai media citing a leaked police memo.

Issued "urgent" and "secret" the memo urges Thai authorities to increase security around venues associated with allies that have joined attacks on IS in Syria, including Australia, the United States, France, Germany and Belgium.

The memo cites intelligence information from Russia that between October 15 and October 31 four Syrian terrorists travelled to the tourist city of Pattaya, two arrived in Phuket – where 20,000 Australians holiday each month – two went to Bangkok and another two went to an unknown destination.