News reports say Japanese police have questioned a university student and several others over alleged plans to travel to Syria to join the Islamic State group.

The reported investigation by Tokyo police would be the first indication of support within Japan for the militant group.

Tokyo Metropolitan Police declined to comment on the reports.

Public broadcaster NHK and Kyodo News service said investigators questioned a 26-year-old male Hokkaido University student and several men who shared a house with him on suspicion they were preparing to go to Syria to fight.

NHK and Kyodo said police searched the house in Tokyo but did not formally arrest the men.