A Jordanian policeman opened fire Monday at a police-training center, killing two Americans and a South African before being shot dead, a government representative said.
State news agency Petra said the three foreign instructors who were killed were on contract with Jordanian police, working at a center outside the capital of Amman. The attacker's colleagues shot the gunman dead after the attack, reports said.
President Barack Obama said a "full investigation" would be set up and the U.S. was "working closely with Jordanians."
Pentagon spokesman Maj. James Brindle told Al Jazeera that the Pentagon was trying to verify information, adding that he could not yet confirm the identity of the two Americans.
Jordan is a staunch U.S. ally and part of the Washington-led coalition that is trying to defeat the Islamic State in Iraq and the Levant (ISIL) in Iraq and Syria, both of which border Jordan.
The country hosts several hundred U.S. trainers who are part of a military program to bolster the kingdom's defenses, including the stationing of F-16 fighter jets that use Jordanian airfields to hit ISIL positions in Syria.
But the kingdom's role in the war against ISIL has caused disquiet among some Jordanians worried about instability at their borders and fearing that a stepped-up role in the campaign might lead to attacks in their country. Jordan's King Abdullah believes ISIL poses an existentialist threat to the kingdom.
Jordanian government officials and the U.S. Embassy in Jordan had no immediate comment on Monday's shooting.