AMMAN:  A car bombing near a Jordanian army post on the sealed border with war-ravaged Syria killed six members of Jordan's security forces and wounded 14 on Tuesday in what the military called a "cowardly terrorist attack."

It was the deadliest attack along the border in recent memory and raised new questions about the pro-Western kingdom's ability to block spillovers from long-running conflicts next door.

The explosion went off at about 5:30 a.m. near a makeshift encampment for tens of thousands of Syrian refugees stranded in the remote desert area on the border, awaiting entry into Jordan.

The military said in a statement that a "cowardly terrorist attack" targeted a military post serving Syrian refugees. The camp is known as Ruqban, the larger one of two that sprang up as growing numbers of Syrians fleeing fighting at home tried to get into Jordan.

There was no immediate claim of responsibility for Tuesday's attack.

The two camps are located along an earthen mound, or berm, that runs along the border in a remote desert area, a few miles from the point where Syria, Jordan and Iraq meet.

The Jordanian military said those killed in Tuesday's attack included four border troops, a member of the civil defense and a public security officer. The statement said 14 were wounded, including nine public security officers.

It was not immediately clear if the attack would disrupt daily deliveries of food, water and other essentials by international aid agencies to the refugees.

With crowds at the berm swelling rapidly in recent weeks, the situation for refugees in the two encampments has become increasingly dire.

Jordan only admits a limited number of refugees every day, citing the need for stringent security vetting. Jordanian officials have said they have evidence that activists of the extremist group Islamic State have infiltrated the two camps and are attempting to slip into Jordan, pretending to be refugees.

Islamic State controls large areas in neighbouring Syria and Iraq. Jordan has fortified border defenses, including with US-funded surveillance systems, to try to stop attackers and infiltrators.

Jordan has also widened a crackdown on IS sympathizers at home, jailing hundreds in the past two years for promoting the group's ideas on social media.

The kingdom is a member of the US-led international military coalition against IS.