Turkey's state-run news agency says the leader of the pro-Kurdish opposition party has been taken to a maximum security prison in the northwestern city of Edirne.

The Anadolou agency said Saturday that Selahattin Demirtas, co-chair of the People's Democratic Party or HDP, was among the 12 party legislators detained overnight for refusal to testify on terror-related charges.

Demirtas, along with fellow co-chair Figen Yuksekdag and seven other lawmakers were formally put under arrest pending trial. The courts released three others on condition they report regularly to authorities.

The private Dogan News Agency said Yuksekdag was taken to a maximum security prison in the northwestern city of Kocaeli.

The government accuses the HDP of being the political arm of its outlawed Kurdish rebels, an accusation the party rejects.