King Abdullah II on Wednesday pardoned six Jordanian jihadist movement members who have spent over a decade in prison, the official news agency reported.
He directed the government to release six who were jailed for plotting terrorist acts and "undermining" national security, the report said, dpa reported.
The Royal Palace declined to give a reason for the decision.
Observers attributed the pardon to what they said was pressure being placed on the monarch by the detainees' tribes.
The Jordanian jihadist movement confirmed that six of its 54 jailed members have been pardoned and noted that the majority of the detainees are being held without charges.
Mousa Abdullat, the defence attorney for the movement, said two of the soon-to-be released men had been serving life sentences for allegedly plotting a bomb attack on a security officer in 2002.
The pardon comes amid tensions between the government and the hardline Islamist group, which is believed to have sent Jordanians to wage "jihad", or holy war, against the regime of President Bashar al-Assad in neighbouring Syria.
Earlier in October, Jordanian authorities announced the arrest of 11 Jordanians suspected of links to al-Qaeda for allegedly plotting attacks on Western embassies and shopping centres in the capital Amman.