Former opposition lawmaker released from prison
Sirri Sureyya Onder was sentenced to three years and six months in jail for spreading terrorist propaganda last December.
He had appealed to the Constitutional Court which ruled on Thursday that his right to freedom of speech had been violated.
As a result, the Istanbul Regional Court's 26th Penal Chamber reconsidered his case and issued a release order, said the source who spoke on condition of anonymity due to restrictions on talking to the media.
The court also ordered a retrial.
Around a dozen HDP lawmakers are currently in prison pending trial for terrorism-related offenses after their parliamentary immunity was lifted in May 2016.
Turkey's government accuses the HDP of having links to the PKK.
In its more than 30-year terror campaign against Turkey, the PKK -- listed as a terrorist organization by Turkey, the U.S. and the EU -- has been responsible for the deaths of some 40,000 people, including women and children.