Jordanian security forces killed several militants and one police officer was also shot dead during a manhunt on Tuesday that involved hundreds of troops in the northern city of Irbid, near the border with Syria, security sources said.
Riot police and special forces took part in the operation, which a security official described as one of the largest sweeps against sleeper cells of sympathisers of hardline groups in recent years.
Another security source said the troops and helicopters were deployed mainly in a Palestinian refugee camp in the heart of the city where most of the wanted fugitives were holed up.
Jordan did not confirm the targets but said security forces had killed a number of "fugitive outlaws" and wounded several others, and least three members of the security forces had been wounded. It later said one security officer was killed.
State television quoted officials as saying the operation was continuing in the city, some 20 km south of the border.
Witnesses reported hearing intermittent gunfire, and roads leading to the area were sealed off by police.
Jordan has been host to big United Nations camps for Palestinian refugees for more than six decades. The squalid camps have long been fertile ground for militants.
Irbid, Jordan's second largest city, also has one of the largest concentrations of Syrian refugees in the kingdom, which hosts over 1.4 million who have fled Syria's near five-year civil war.
Jordan has put on trial and sentenced dozens of militants who returned from Syria, some of whom were recruited by Syria's Al Qaeda offshoot Nusra Front or the DAESH terrorist group.
It has also arrested dozens of sympathisers who show support for the group on social media.
It was not immediately clear which group the militants being sought represented. One source said they were suspected of being from DAESH; another did not specify.
Another security source told Reuters on condition of anonymity that the covert operation undertaken by the intelligence apparatus targeted mainly members of DAESH, with at least 30 suspects rounded up.
King Abdullah, a US ally who has safeguarded his country's peace treaty with Israel, has been among the most vocal regional leaders voicing alarm about the threat from DAESH, which has taken territory in Syria and Iraq.
Jordan's military has waged sorties against DAESH hideouts in Syria and the kingdom is part of the US-led coalition against the group.
Jordan has long been vigilant about the risk of militant strikes in a country that has sustained attacks before, notably bombings on Amman hotels by al Qaeda-linked militants during the US occupation of Iraq.