Police are questioning a 26-year-old Japanese Muslim on suspicion of trying to join Islamic State rebels in Syria, media reports and the top government spokesman said Tuesday.

The man, a student at Hokkaido University, had reportedly planned to fly to the Middle East this week to fight with the rebel group, which has cut a swathe through Syria and Iraq.

The student told police he “was planning to travel to Syria so as to join Islamic State to work as a fighter”, the Mainichi Shimbun and other media reported.

He hatched the plan after spotting a job advertisement posted at a second-hand bookshop in Tokyo.

The poster, which was shown on NHK, directed people interested in working in Syria to the shop clerk.

It said a monthly wage of 15,000 RMB (around $2,400) was payable for people “not afraid of violence” to work alongside Uighurs in Syria.

Uighurs are the mainly-Muslim inhabitants of China’s northwest Xinjiang province. Beijing is facing mounting violence there, which it has blamed on separatists it says have been radicalized through contact with overseas-based terror groups.

Most scholars remain sceptical of China’s claims, however, with some arguing that Beijing exaggerates the threat to justify its hardline measures in Xinjiang.

There have been no confirmed reports of Uighurs fighting alongside Islamic State in Syria or Iraq.

No Chinese language ability was necessary, the advert said. There was no explanation of what the work entailed, or why the wage would be paid in the Chinese currency.

Hundreds of mostly young men have travelled from Europe and North America to join forces with the brutal group of radicals, which has declared an Islamic “caliphate”. However, this is believed to be the first attempt by a Japanese.

Japan has a tiny Muslim population, made up largely of relatively recent immigrants, and little history of home-grown religious extremism.

Detectives are also investigating the advertiser, the Yomiuri Shimbun said, without giving details of his or her identity.

An employee at the bookstore was quoted as saying: “I introduced several people to a former university professor of Islamic law”. The academic denied advising anyone to join the jihadis, the Asahi Shimbun said, without identifying him or her.

The relationship between the bookstore and the advertiser was not immediately clear.

A police spokesman declined to comment on the case.

“We are aware that police are investigating the case based on criminal law but we decline to comment further as it is still under investigation,” Chief Cabinet Secretary Yoshihide Soga told reporters, asked about the move.

Under Japanese law, it is illegal to prepare or plot “to wage war against a foreign state in a personal capacity”, Kyodo News reported, adding the offence carried a maximum five year jail sentence. SAPA