ISTANBUL, Dec. 21 (Xinhua) -- The Turkish police on Friday detained at least another eight foreigners in Istanbul for their suspected links to the Islamic State (IS) militant group, state-run Anadolu Agency reported.

Simultaneous operations were launched in nine districts across the city to capture the suspects, who were allegedly planning terror attacks, Anadolu said.

Police also seized illegal documents, books and digital materials during the raids.

On Wednesday, 19 foreigners were captured in Istanbul for their suspected links to the IS.

Over the years in Turkey, more than 300 people were killed in deadly attacks blamed on the militant group.