Bahrain's king has pardoned 1,584 people facing criminal and "riot" charges, state media said Monday, in the largest such mass release in the Gulf nation in years.

The pardons cover "those convicted for riot and criminal cases", and were announced as Bahrain's King Hamad bin Isa Al Khalifa marks 25 years since his ascension to the throne, BNA added.

Sayed Alwadaei, advocacy director for the Britain-based Bahrain Institute for Rights and Democracy (BIRD) said political prisoners were likely included in the pardon "as the term 'riot' refers to those who demanded political change".

BIRD said the latest royal decree marks the "highest number of pardoned prisoners since the pro-democracy uprising in 2011," when anti-government protests triggered a state crackdown.

The decree also comes ahead of the Muslim holiday of Eid al-Fitr which marks the end of the fasting month of Ramadan, an occasion that often elicits prison pardons from Gulf leaders.

In the wake of the Covid-19 pandemic, Bahrain's interior ministry announced in 2020 the release of 1,486 prisoners including 901 who had received royal pardons on "humanitarian grounds".