Iran says it has released temporarily more than 1,000 foreign prisoners due to the coronavirus outbreak, following criticism by UN human rights experts.

"What Iran has done in guaranteeing prisoners' health and granting furlough to them is a significant move" compared with what other countries have done, said Gholamhossein Esmaili, a spokesman for the country's judiciary.

British-Iranian woman Nazanin Zaghari-Ratcliffe, who was among 100,000 prisoners temporarily released last month, had her leave extended until May 20, her lawyer, Tulip Siddiq, said on April 21.

Zaghari-Ratcliffe was serving a five-year jail term for sedition after being arrested in 2016 during a holiday on the accusation that she was plotting to overthrow the government.

Her family says she was in Iran to visit relatives and denied that she was plotting against Iran.

Zaghari-Ratcliffe worked for the Thomson Reuters Foundation, the charitable arm of the news agency.

Tehran's announcement on April 21 came after a panel of UN human rights experts last week urged the expansion of the list of prisoners temporarily released over the COVID-19 outbreak to include "prisoners of conscience and dual and foreign nationals."

The 100,000 -- mainly Iranian -- prisoners released temporarily last month were freed initially until April 19. Authorities then extended their furlough until May 20.

Foreign prisoners including French-Iranian Fariba Adelkhah and Iranian-American businessman Siamak Namazi and his father, Mohammad Bagher Namazi, are believed to still be in detention.

Iran has been struggling to contain one of the world's worst outbreaks of the coronavirus since reporting its first cases on February 19.

On April 21, Health Ministry spokesman Kianush Jahanpur announced 88 more deaths over the past 24 hours, bringing the total to almost 5,300 out of a total of more than 83,500 people confirmed as infected.

Many analysts, however, say the true number may be higher due to poor reporting methods, the government's lack of transparency, and a lack of testing.

With reporting by AFP and Reuters