Five Jordanian intelligence employees were killed in an attack on their office in a Palestinian refugee camp, north of the capital Amman on Monday, government spokesman Mohammed Momani said.
"The intelligence agency office in the Baqa'a camp was the target of a cowardly attack shortly before 7:00 am (0400 GMT) today that left five agents dead," Momani said.
He added that the assailants, whom he described as terrorists, killed three guards, a handyman and a receptionist, but didn't clarify how they carried out the attack.
He suggested the attackers were Islamic militants, saying they displayed the "criminal behaviour of people who are outside of our religion."
No group immediately claimed responsibility for the attack.
Security authorities are currently investigating the incidents and will announce the details later, Momani said.
Baqa'a is the the largest Palestinian camp in Jordan, run by the UN relief agency for refugees UNRWA.
Such attacks are rare in pro-Western Jordan, a key member of the US-led military coalition against Islamic State extremists in neighbouring Syria and Iraq.
One of its pilots was captured by IS militants when his plane went down in Syria in December 2014. IS later released gruesome footage of him being burned alive.
Jordan has also opened up the Prince Hassan airbase, northeast of the capital, to other members of the US-led coalition taking part in the air war.
In March, Jordanian authorities announced they had foiled an IS plot to carry out attacks in the kingdom in an operation that led to the deaths of seven militants and one security officer.