The top public prosecutor in Ankara on Wednesday demanded that the leftist opposition Peoples' Democratic Party (HDP) be dissolved over its alleged links to the Kurdistan Workers' Party (PKK).

The 609-page indictment put before the Constitutional Court accuses the HDP of being a threat to the "indivisible integrity of the state" and seeks to ban more than 600 party members from engaging in politics for five years, AFP reported.

The US State Department said the ban would "further undermine" democracy in Turkey and the European Union said it was "deeply concerned" since the party's closure "would violate the rights of millions of voters in Turkey".

"Criminal proceedings against numerous MPs and members of the HDP are all part of a development that calls into question the rule of law in Turkey," a German foreign ministry spokesman added in Berlin.

The Turkish foreign ministry responded by saying that comments from "some countries" it did not name "were incompatible with the principle of the rule of law".

"We invite those... who dare to meddle in our domestic affairs to respect the judicial process led by independent courts," it said.

Turkey is under fire from Western governments over the independence of its judiciary.

Critics accuse President Recep Tayyip Erdogan of stacking the courts with supporters and using them to muzzle opponents since surviving a failed coup attempt in 2016.

The HDP in particular has been on the radar of Turkish officials over its alleged links to the PKK.

The PKK is listed as a terrorist organization by Ankara and its Western allies.

The HDP has seen dozens of its mayors dismissed over alleged terror links.

The party's former co-chair Selahattin Demirtas -- a two-time rival to Erdogan in presidential elections -- has been kept in detention since 2016 despite calls from European Court of Human Rights demanding his release.

The chief public prosecutor alleges in his indictment that the HDP is "organically" linked to the PKK.

Erdogan's press aide Fahrettin Altun tweeted on Wednesday that "it is an indisputable fact that HDP has organic ties to PKK".

Turkey's parliament on Wednesday also stripped HDP lawmaker and rights defender Omer Faruk Gergerlioglu of his seat over a social media post that the courts ruled had promoted terrorist propaganda.

The post featured a news article urging the government to take a step toward peace with the PKK.

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