Five people, including two American civilian contractors, have been shot dead by a Jordanian police officer at a US-funded security training centre near Amman.

The Jordanian embassy in Washington said two Americans, a South African and two Jordanians were killed in the attack at the King Abdullah Training Centre, along with the shooter.

Four others were being injured, it added.

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US president Barack Obama said he was treating the attack very seriously and a full investigation was under way.

The gunman’s background and motive were not immediately known. He was killed in a shootout after the incident.

Jordanian officials told news agencies the gunman was a police captain and co-trainer at the facility on the outskirts of the country’s capital, which mainly trains Iraqi and Palestinian police officers.

The US embassy said it was “premature” to speculate on motive at this point.

Jordan is a staunch US ally in the Washington-led campaign against Islamic State (IS) militants, who hold large areas of neighbouring Syria and Iraq, a position that leaves the kingdom vulnerable to jihadist attacks.

“The investigation is ongoing and it is premature to speculate on motive at this point,” the US embassy in Jordan said in a statement.

The country hosts several hundred US trainers who are part of a military program to bolster the kingdom’s defences, including the stationing of F16 fighter jets that use Jordanian airfields to hit Islamic State positions in Syria.

But the kingdom’s role in the war against IS 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 Islamist attacks in their country.

King Abdullah believes fervently that ultra hardline jihadists pose an existentialist threat to the kingdom.

The attack came on the 10th anniversary of three Al Qaeda suicide bombings of high-end luxury hotels in Amman in 2005, which killed 60 people and wounded 115 more, in the worst militant attack in the history of Jordan.

– ABC