Omer Faruk Gergerlioglu, an outspoken rights defender from the Peoples' Democratic Party (HDP), was handed a two-and-a-half-year prison sentence in April for spreading "terrorist propaganda" online over a post he shared in 2016 before he was elected an MP.

He had commented on a story which reported on outlawed Kurdish militants calling on the Turkish state to take a step towards peace.

He was held in Sincan prison on the outskirts of the capital Ankara, having been stripped of his parliamentary seat and immunity.

Last week, the top Constitutional Court ruled that Gergerlioglu's rights to be elected and engage in political activity had been violated.

The lower court on Tuesday complied with the top court's verdict and ordered the ex-lawmaker's release, HaberTurk television reported.

Shortly after the ruling, Gergerlioglu was let out.

"He is free," his son Salih tweeted, sharing a picture of him sitting in the back seat of a car.

The HDP, the third-largest party in parliament, has been on the authorities' radar for years with the arrest of several of its lawmakers and leaders, including charismatic former co-chair Selahattin Demirtas.

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

The HDP rejects any links to terror and blasts the crackdown as a "political coup".

The 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.