Jordan has closed its northern and northeastern borders with Syria after a suicide attack killed six Jordanian security forces and wounded another 14 near a Syrian refugee camp. The suicide bomber reportedly drove an explosive laden truck and detonated it at an army post near Rukban, an isolated desert border with Syria, on Tuesday (21 June).

On the same day, General Mishal al Zibn, the chief of staff of the Jordanian army, declared the border a "military zone" and said any movement will be treated without leniency.

"Any vehicle and personnel movement within these areas that move without prior coordination will be treated as enemy targets and dealt with firmly and without leniency," he said.

King Abdullah II vowed to "respond with an iron fist" against anyone who wants to harm Jordanian security or borders.

"Such heinous terrorist acts will only make us more determined to carry on with our fight against terrorism and its groups who plotted in the dark against the men who protect the country and its borders," The Guardian quoted him as saying.

As of yet, no one has claimed responsibility for the attack, but Jordan is an important member of the US-backed coalition combating the Islamic State (Isis) in Syria and Iraq.

International relief agencies said authorities also suspended humanitarian aid to tens of thousands of refugees stranded on the other side of the border.

The suicide attack comes almost two weeks after gunmen shot dead five Jordanian intelligence agents, at a Palestinian refugee camp near Amman. A suspect was later arrested, but a gagging order has been in place while investigation into the case continues.