DIYARBAKIR - Turkey on Friday jailed the two co-leaders of the country's main pro-Kurdish party and several other MPs, in an unprecedented crackdown as a deadly bombing killed nine in the Kurdish-dominated southeast.

A court in the southeastern city of Diyarbakir remanded in custody Peoples' Democratic Party (HDP) co-leaders Selahattin Demirtas and Figen Yuksekdag after they were detained along with 10 of its MPs, the state-run Anadolu news agency said.

Including Demirtas and Yuksekdag, seven HDP MPs have so far been placed under arrest by the courts pending trial.

The United States and European Union both raised alarm over the arrests, which marked a new escalation of the clampdown under the state of emergency imposed in the wake of the July 15 coup attempt.

Hours earlier, a blast blamed on the outlawed Kurdistan Workers' Party (PKK) struck outside a police station nearby in the Baglar district of Diyarbakir, Turkey 's main majority-Kurdish city. Eight people were killed, including two police, and over 100 were wounded, Prime Minister Binali Yildirim announced, saying the PKK had again showed its "ugly face". Anadolu said another civilian later died of their wounds.

With tensions again escalating in Turkey nearly four months after July's failed coup, authorities slapped restrictions on social media including messaging services like WhatsApp.

Yildirim confirmed the move, saying such measures were imposed from "time to time" as a precaution and would be lifted once the danger had passed.

The turbulence also battered the Turkish lira. It was trading at 3.17 to the dollar, a new historic low and a loss in value of nearly two percent on the day.

The arrest of the HDP leaders marked a new stage in the crackdown on leading pro-Kurdish politicians as President Recep Tayyip Erdogan wages a remorseless battle to destroy the PKK.

Demirtas has been charged with "membership of an armed group" - a reference to the PKK - while Yuksekdag is charged with making "terror propaganda" for the group, Anadolu said. The HDP said in a statement that the goal of the measures was to shut down the party, but it vowed not to surrender to these "dictatorial policies". "It means the end of democracy in Turkey ," the party said. In a handwritten statement read by his lawyers, Demirtas said he was the victim of a "civilian coup by the government and the palace".

After his jailing he managed to shout, "We will definitely win!".  The Turkish of this phrase, #MutlakaKazanacagiz, immediately became a top-trending hashtag.  EU foreign policy chief Federica Mogherini said on Twitter she was "extremely worried" over the detentions and would call a meeting of EU ambassadors in Ankara. US Assistant Secretary of State Tom Malinowski said on Twitter that Washington was "deeply troubled that government of Turkey has detained HDP leaders and other MPs while blocking internet access".

German Foreign Minister Frank-Walter Steinmeier summoned Turkey 's envoy to the foreign ministry in Berlin, a ministry source said, adding Germany "could not remain silent." As as well as Demirtas and Yuksekdag, five others were also placed under arrest by the courts including the head of the HDP's parliamentary faction Idris Baluken.

However three lawmakers Ziya Pir, Imam Tascier and Sirri Sureyya Onder were allowed to go free under judicial control - the Turkish equivalent of bail - with hearings still in progress for the others.

The raids come as Turkey remains under a state of emergency imposed in the wake of the failed coup, which critics say has gone well beyond targeting the actual coup plotters.

Thirteen staff from the opposition Cumhuriyet newspaper, including the editor-in-chief, were detained on Monday, further heightening strains in Turkish society. The two co-mayors of Diyarbakir were also detained last month.

Amnesty International said that the arrests of the MPs "marks the latest escalation in the onslaught on dissent amid Turkey 's state of emergency."

Tensions have surged in the Kurdish-dominated southeast since a fragile ceasefire declared by the PKK collapsed in 2015, leading to a resumption of deadly attacks on the security forces.

The HDP, the third largest party in parliament, seeks to promote the cause of Turkey 's Kurdish minority and defend the rights of Kurds as well as those of women, gays and workers.

The charisma in particular of Demirtas - dubbed the "Kurdish Obama" by some admirers after the US president - earned the party success at the ballot box but also made him an arch rival of Erdogan.

Authorities accuse the party of being a PKK front and failing to distance itself from terror, claims it has always vehemently denied.