The authorities in Venezuela have freed the former presidential candidate Manuel Rosales, along with five student activists held since 2014.
Mr Rosales, who stood against Hugo Chavez in 2006, was arrested over corruption charges in October 2015 after returning from exile in Peru.
The activists were arrested in 2014, during protests calling for the removal of President Nicolas Maduro from power.
Opposition leaders say about 100 opposition activists remain in prison.
Opposition groups named the released activists as Skarlyn Duarte, Yeimi Varela, Nixon Leal, Angel Contreras and Gerardo Carrero, the AFP news agency reported.
Mr Carrero led a group of anti-government protesters who camped for weeks outside the UN offices in Caracas, Venezuela's capital.
Mr Rosales, of the small Nuevo Tiempo party, announced his release from house arrest on his Twitter account:
"I inform you the people of Venezuela, that I have been released along with other political prisoners," he posted in Spanish.
"We continue in the struggle for the release of all political prisoners and the return of the exiles," he added.
Mr Rosales, a former governor of the state of Zulia, fled to Peru in 2009 amid corruption allegations, which he said were politically motivated.
He was moved from prison to house arrest in October.
Venezuela is struggling with a serious economic crisis, which the opposition blames on failed socialist policies of Mr Chavez and his successor, Mr Maduro.
Dissident leaders had demanded the release of Mr Rosales, and freedom for other opposition leaders, during negotiations with the government.