“Security forces arrested the Iraqi suspect while he was driving his car,” a security source said on condition of anonymity, without saying where he had been arrested.

The unnamed Iraqi was one of four suspects being sought by authorities who ordered a security clampdown following Friday’s attack which was claimed by an Al Qaeda linked group.

Three Katyusha rockets were fired from Aqaba, one of them missing two US warships anchored nearby but killing a Jordanian soldier as it smashed into a warehouse. No US troops were harmed in the attack.

Another landed close to the airport in the adjacent Israeli resort of Eilat. The third struck a site near a military hospital.

The attack was claimed in an Internet statement by a group which previously said it was behind deadly bombings on resorts in Egypt over the past year.

The Al Qaeda Organisation in the Levant and Egypt, in an Internet statement whose authenticity could not be confirmed, said that its “mujahedeen” had returned “safely to base” after the attack.

Police had on Saturday installed roadblocks at entry and exit points to the bustling resort city, checking through vehicles and taking some individuals to one side for further scrutiny.

A total of twelve roadblocks were on the 350 kilometre (220 mile) road between Aqaba and Amman, while checkpoints also appeared in the capital.

Jordanian Interior Minister Awni Yervas refused to disclose the identities of the Arab suspects but did reveal that rocket launchers were found in the depot from where the Katyushas were fired.

“The enquiry is continuing in secret and the authorities will only make public information that does not cause harm to the investigation... Rocket launchers have been found in the depot,” he said.

King Abdullah II, absent from the country on a visit to Russia, condemned what he called a “criminal attack”, officials said.

Jordan would “continue its message of justice and tolerance and continue to show a true image of Islam that the terrorists were seeking to deform,”  he added.

However, the peak of the tourist season in Aqaba appeared to be unaffected on Saturday, with the airport staying open and hotels insisting that none of their clients had cancelled or left early.