A Turkish court placed the two leaders of a major pro-Kurdish opposition party under arrest on Friday in a dramatic widening of a political crackdown that followed July’s failed military coup that will raise concerns about the future of Turkey’s parliamentary democracy.

Police detained the co-chairs of the Peoples’ Democratic Party (HDP), Selahhatin Demirtas and Figen Yuksekdag, early on Friday morning along with nine other lawmakers. The measures against pro-Kurdish officials more than three months after president Recep Tayyip Erdogan narrowly survived an attempt by part of the military to seize power on July 15 could also open a new season of conflict with armed Kurdish insurgents. Hours after the arrests, a car bombing reportedly killed at least eight people in the city of Diyarbakir, the largest city in the Kurdish-majority southeast of Turkey.

Bringing together a diverse coalition on a platform of democracy and minority rights, the HDP catapulted into parliament in June 2015 embodying hopes for a more pluralistic brand of politics in Turkey and now controls 59 seats in Turkey’s 550 member Grand National Assembly, making it the parliament’s third largest. A charismatic politician whose broad appeal transcended his Kurdish heritage, Demirtas was hailed as a “Kurdish Obama.”

According to the Interior Ministry, Demirtas and the other members of parliament were detained for failing to appear in response to a prosecutor’s summons seeking their testimony in an investigation. Arrest warrants have been issued for two other members of parliament who are currently outside of Turkey, according to the Interior Ministry. In May parliament passed a law that stripped lawmakers of their immunity from prosecution, a move many feared would pave the way for charges against pro-Kurdish officials over alleged ties to Kurdish militants.

Human rights groups sounded a fresh note of alarm Friday morning, as news of the arrests emerged. “Detaining members of parliament is an assault on the fundamental principles of democracy and on the right to political representation,” Emma Sinclair-Webb, a Turkey researcher for Human Rights Watch, told TIME. Demirtas and his co-leader are to be held in detention pending a possible trial.

The arrests followed weeks of expanding repression against institutions and officials critical of Erdogan’s government. On October 30, police arrested the two co-mayors of the majority Kurdish city of Diyarbakir, charging one of them with belonging to a terrorist organization. On October 31, authorities detained the editor and several top writers for the newspaper Cumhuriyet, a bastion of secular liberal journalism in Turkey for decades.

The HDP denounced the arrests in a hastily organized news conference on Friday morning in Ankara. “Everyone who supports peace and democracy must speak now. Tomorrow will be too late,” said party official Ayhan Bilgen, according to a message published on the party’s Twitter page. Lawmaker Mithat Sancar said the party was calling for “solidarity” with his detained colleagues in order to “prevent civil war.” The organization has called for a return to peace negotiations and denies ties with PKK militants. Demirtas’ older brother spent 12 years in a Turkish jail for membership the PKK’s youth branch and is now believed to be with the organization somewhere in Iraq or Syria.

In a message sent via his lawyer in an email on Friday evening, Demirtas said, “We are facing a different stage of the ongoing civil coup led by the government and the palace. My colleagues and I will continue to stand strong against this unlawful coup everywhere and at every stage.”

The arrests heightened anxieties about stability in Turkey, a NATO member and a U.S. ally that in years past enjoyed a reputation as a bulwark of calm in a turbulent Middle East. The Turkish state is has engaged in an intermittent war with the outlawed militants of the Kurdistan Workers Party (PKK) for some 30 years. Peace negotiations crumbled in 2015, triggering a resumption of fighting in the Kurdish towns of Turkey’s southeast, displacing an estimated 350,000 people and leaving at least 920 people dead as of June 2016, according to International Crisis Group.

In a video that surfaced on Friday, PKK commander Murat Karayilan said the group would intensify its struggle with the Turkish state in response to the arrest of the lawmakers. In addition to the PKK, Turkey is also battling ISIS militants who have been blamed for a series of attacks on civilians over the last year and a half, culminating with a deadly assault on Istanbul’s main airport in June.

Increasing the sense of tension, Turkish authorities blocked access to social media networks including Twitter and WhatsApp, which represent a key means of spreading information under a state that increasingly restricts reporting by the traditional news media. In Diyarbakir, Internet access was completely shut down on Friday morning, according to a resident of the city.

On the night of July 15, a portion of the military attempted to overthrow Erdogan’s elected government, leaving more than 200 people dead and bombing the parliament building in the process. The coup failed, leaving Erdogan to consolidate his hold on power. Thousands of people were arrested and tens of thousands of government employees suspended from their jobs in connection with an investigation into the coup plot. The government dismissed roughly a third of the military’s top leadership.

The military coup attempt spurred a fleeting moment of unity in Turkish politics as all four major parties supported the government in fierce opposition to the coup plot. Demonstrators stood in the streets of Istanbul and Ankara in opposition to military vehicles mobilized by the coup plotters. Now with the arrest of pro-Kurdish lawmakers, any hope of salvaging the short-lived consensus that emerged on the night of the coup.

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