More than 500 political prisoners are thought to still be in jail, despite the releases since the amnesty law was brought in.
US President Trump has made clear his desire to change Cuba's leadership and has placed the country under an oil embargo.
The UN is deeply concerned by allegations there have been incidents of torture after Nicolás Maduro's ouster.
Mikola Statkevich, who spent more than five years in prison in his native Belarus, is now recovering from a stroke at home, his wife says.
An NGO says hundreds of people remain behind bars despite US pressure US to speed up their release.
Nobel Peace Prize winner María Corina Machado says political leader Juan Pablo Guanipa was taken by force in Caracas.
The Justice First party leader is among 18 political prisoners to be freed by the interim government on Sunday.
Southern & Eastern Europe correspondent Sarah Rainsford reports from Lithuania, where some of the released prisoners were taken.
El Salvador proposes exchanging 252 US-deported Venezuelans for the same number of "political prisoners" in Venezuela.
