Austrian police say they have detained eight people on suspicion of belonging to a terrorist organisation through possible connections to so-called Islamic State.

There were 800 police officers involved in the operation, which involved searching several apartments and mosques in Vienna and Graz.

The raids come less than a week after police in Vienna detained a 17-year-old they described as belonging to "radical Salafist" circles.

However, the police statement said Thursday's raids had been planned for "a longer time," suggesting no immediate link.