Jordan has declared its borders with southern Syria a "military zone" after a suicide attack claimed the lives of six soldiers near a refugee camp housing thousands of Syrians.
General Mishal al Zibn, the chief of staff of the Jordanian army, declared the porous northern and northeastern border on Tuesday a closed military zone, warning that any movement in the area would 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," the army statement said.
International relief workers said the Jordanian authorities had also suspended all humanitarian aid to the area and that this could put the lives of refugees at risk.
At least six people were killed and 14 others injured earlier on Tuesday in attack carried out by a suicide car bomber in in al-Rukban, a desolate desert area that has become home to about 70,000 Syrian refugees.
The victims were mostly army personnel, according to an earlier army statement.
Jordan's King Abdullah II condemned the attack and threatened to "strike with an iron fist whoever assaults or attempts to harm it or its borders".
The attack came two weeks after five Jordanian intelligence agents were killed when a gunman stormed the General Intelligence Directorate office in Ain el-Basha near the Palestinian refugee camp of al Baqa'a.
No information on the motives or affiliation of the attacker has been released by the Jordanian authorities.
The Islamic State of Iraq and the Levant (ISIL, also known as ISIS) controls large areas in neighbouring Syria and Iraq. Jordan has fortified border defences to prevent attacks and infiltration attempts.
Jordan has also widened a crackdown on ISIL sympathisers 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 ISIL.
