Omer Faruk Gergerlioglu, an outspoken rights defender from the Peoples' Democratic Party (HDP), was handed a two-and-a-half-year prison sentence for spreading "terrorist propaganda" online.

In March, the parliament revoked his seat and immunity from prosecution after a court upheld his controversial conviction over a social media post.

Gergerlioglu then applied to the top court seeking to annul the parliament decision.

He has rejected the accusations, and his expulsion from parliament was criticised by numerous campaign groups and Western governments.

"The Constitutional Court ruled that the rights of my father were violated," his son Salih tweeted, adding: "He is going to be released."

Turkish media reported that his rights to be elected and engaged in political activity, as well as personal rights and personal security had been violated.

The HDP, the third-largest party in the Turkish parliament, has been under a constant crackdown since 2016 with the arrest of several of its lawmakers and leaders, including its charismatic former co-chair Selahattin Demirtas.

Last month, the Constitutional Court put the party on trial over its alleged links to outlawed Kurdish militants, setting the stage for its possible shutdown.

The outlawed Kurdistan Workers' Party (PKK) has been waging an insurgency since 1984 that has killed tens of thousands and is listed as a terrorist organisation by Ankara and its Western allies.