The constitutional amendment was passed with a two-thirds majority on Friday, meaning there was no need for the issue to be put to a referendum. In the decisive round of voting, 376 members of the 550-seat parliament were in favor, 140 voted against and other members abstained.

"They will have to arrest us, take us by force. We will resort to all possible measures to challenge the decision, including taking it to the constitutional court," the chief of the People's Democratic Party (HDP) Selahattin Demirtas, said. Demirtas is one of 50 party members - out of its 59 in parliament - who will lose the immunity hitherto enjoyed by all Turkish MPs.

The HDP has backed minority rights in Turkey, including for the Kurds. It has denied accusations that it is the political arm of the outlawed Kurdistan Workers' Party or PKK. Turkish security forces have been battling the PKK for almost the past year after a ceasefire which paused more than three decades of on-off armed conflict.

To take effect, the bill still needs to be published and approved by Turkish President Recep Tayyip Erdogan, who has spoken strongly in favor of it.

"My nation does not want to see guilty lawmakers in this country's parliament. Above all it does not want to see those supported by the separatist terror group in parliament," Erdogan told a crowd in the Black Sea town of Rize on Friday.

Members of other parties including the opposition Republican People's Party (CHP) are also at risk of prosecution. In total, 138 MPs have had police dossiers opened on them.

Critics see the move as a way for President Recep Tayyip Erdogan to push the HDP out of parliament, strengthen the ruling Justice and Development Party (AKP) - of which Erdogan is a founder - and clear the path for further new laws to empower the presidency.

Concern from Europe

The measures have caused concern in Europe, which is relying on Turkey's cooperation to stop refugees and migrants using illegal means to enter the EU. It comes amid concern over Ankara's record on human rights and press freedom.

In a joint statement, the EU's foreign policy chief Federica Mogherini and commissioner Johannes Hahn expressed "serious concern" about the vote.

"In line with relevant international recommendations, immunity must apply to all on a non-discriminatory basis and decisions on lifting immunity must be based on the merits of each specific case, according to transparent criteria and not subject to any political considerations," Mogherini and Hahn said.

European Parliament President Martin Schulz said the vote directly targeted AKP opponents and amounted to a "blow to Turkish democracy and political freedom." He warned of a widening gulf with "European norms and values."

German Chancellor Angela Merkel's spokesman also raised concerns:

"For the domestic stability of every democracy, it is important for every relevant group in society to be also represented in parliament," Steffen Seibert told reporters, adding that the Chancellor would raise the issue with Erdogan on the sidelines of a humanitarian summit in Istanbul.

se/jm (Reuters, AP, dpa, AFP)