Police say they have detained 165 suspected members of the Turkish branch of a radical Islamic movement in a nationwide crackdown.

A statement from the Istanbul police headquarters says the suspected members of the Hizb ut-Tahrir group were detained in simultaneous raids in 21 provinces on Friday.

Monday's statement says the operation was launched in coordination with Turkey's national intelligence agency.

It said police seized arms, hundreds of T-shirts emblazoned with a slogan calling for the establishment of one large state ruled by Islamic laws, as well as maps and flags of such a state.

The Hizb ut-Tahrir group is banned in Turkey.