The Venezuelan government says it is releasing 80 people detained during demonstrations as a Christmas goodwill gesture, BBC reported.
By Sunday morning 36 prisoners had been released, a local NGO said. About 150 further detainees remain in custody.
It follows a request from Venezuela's opposition to release those it described as "political prisoners".
But President Nicolas Maduro says the activists have been jailed on legitimate charges.
On Thursday the regional trade group Mercosur also called for the prisoners to be released.
More than 120 people have been killed during anti-government protests this year.
Thirteen of the released prisoners appeared on state TV, with senior official Delcy Rodriguez wishing them a happy Christmas.
The freed activists included former provincial mayor Alfredo Ramos.
"It was a tough ordeal, very difficult. It was an arbitrary detention, unjust. I didn't commit any crime," he told local media.Venezuelan opposition leader Leopoldo Lopez remains under house arrest in the capital Caracas. He is accused of leading violence in 2014.
The opposition accuses Mr Maduro and his predecessor, the late Hugo Chavez, of destroying the country's economy with their socialist policies.
Venezuela has one of the world's highest inflation rates and for years has suffered from a shortage of basic goods, including medicines.
Mr Maduro is also accused of sidelining Venezuela's elected parliament by setting up a new constituent assembly to approve his policies.
He is expected to run for a second term next year and has banned some opposition parties from taking part.