Videos shared on social media showed tearful reunions in a courtyard outside Jau prison where black-clad women waited to spot their sons and husbands among those freed.

Bahrain's King Hamad bin Isa Al Khalifa issued a royal decree pardoning 457 inmates to foster "social cohesion" and celebrate his 25 years on the throne, the official Bahrain News Agency said late on Wednesday.

The move came five months after a pardon of more than 1,500 inmates , the biggest in years.

BNA did not specify who is covered by Wednesday's pardon but the Britain-based Bahrain Institute for Rights and Democracy (BIRD) said political prisoners were included in the latest releases, which started on Thursday.

Sayed Alwadaei, BIRD's advocacy director, said around 100 inmates have been released so far, calling the pardon "a significant step forward".