Turkey arrested two MPs from the main pro-Kurdish party on Tuesday, including its chief spokesman, the latest move in a crackdown on the group ahead of a vote on changing the constitution.
Ayhan Bilgen -- spokesman for the Peoples' Democratic Party (HDP) and an MP representing the eastern province of Kars -- was remanded in custody ahead of trial after he was detained by police at an Ankara airport on Sunday and taken to the Kurdish-majority city of Diyarbakir in the southeast.
The state-run Anadolu news agency reported that he was arrested on charges of "membership in an armed terror organisation."
Another prominent HDP lawmaker, its legal expert Meral Danis Bestas, was also placed under arrest after being detained at her home in Diyarbakir.
But the party said Bilgen's arrest was meant to prevent the HDP from campaigning against constitutional changes that would dramatically expand President Recep Tayyip Erdogan's powers in a referendum set for April.
"The arrest of our party spokesman Ayhan Bilgen is to block our referendum work but you cannot turn down the volume of 'NO,'" the HDP wrote on its Twitter account.
The arrests raised the number of HDP MPs behind bars on terror charges to 12, including the party's co-chairs Selahattin Demirtas and Figen Yuksekdag. The party holds 59 of the 550 seats in parliament.
Bilgen had become the public face of the party in the absence of the co-leaders.
Turkish prosecutors are demanding up to 142 years in prison for Demirtas on charges of links to the outlawed Kurdistan Workers' Party (PKK), which has waged a bloody insurgency against the Turkish state since 1984.
Demirtas and other MPs have denied any links to the PKK, listed as a terror group by Turkey and its Western allies, and denounced the case as political.
In another move, police detained a member of the secular opposition Republican People's Party (CHP), Sera Kadigil, on accusations of "insulting the president", "publicly denigrating religious values and inciting hatred" through a series of social media posts.
These included a post questioning slogans like "martyrs never die", which have been much repeated as the army presses offensives against Kurdish militants and jihadists.
Kadigil, a lawyer and a member of the party's assembly, was held by the police after her client's hearing at an Istanbul courthouse, Anadolu reported.
CHP lawmaker Baris Yarkadas, who appeared at the Istanbul courthouse in support of Kadigil, argued that the detention was timed to coincide with the referendum campaign, saying the tweets in question dated to 2015.
"How interesting it is that Kadigil's tweets -- ignored since 2015 -- were all of a sudden taken out of the archives and began to be discussed as the date for referendum draws closer," he said.