Hundreds of Turkish riot police using teargas forced their way into the Ankara headquarters of the main CHP opposition party on Sunday after a court dismissed its leadership, AFP journalists saw.

Party members had blocked the building's entrances, defying the court order issued Thursday as part of an official probe against the Republican People's Party (CHP).

A prominent rights NGO, Human Rights Watch, on Saturday warned that President Recep Tayyip Erdogan's government was undermining Turkish democracy with "abusive tactics" against the CHP.

Last year, Turkish authorities jailed Erdogan's main political rival, Istanbul mayor Ekrem Imamoglu, who was the CHP's candidate for the presidential election due in 2028.

The court order on Thursday cancelled the 2023 victory in party elections of CHP head Ozgur Ozel and named its former chair Kemal Kilicdaroglu -- a lacklustre figure who chalked up a string of electoral defeats -- as interim leader. 

Ozel on Sunday had defiantly declared on social media that "We will not leave here!"

Kilicdaroglu's backers then tried to push their way in, before police received orders to step in and take the building.

Last year, similar scenes took place in Istanbul, when the courts named an administrator to take charge of the regional CHP offices.

© Agence France-Presse