'Married couple' among Amman bombers

The statement, which identified the bombers, came as more than 120 people were arrested in Jordan in a series of security raids.

In a highly unusual move, the group, led by the Jordanian-born Abu Musab al-Zarqawi gave a detailed account of Wednesday night's attacks. The four who blew themselves up, killing 57 others, were named as Abu Khabib, Abu Muaz, Abu Omaira and Om Omaira. It said "they vowed to die and they chose the shortest route to receive the blessings of God".

The authenticity of the claim could not be independently verified. But it was posted on a site normally used by al-Qa'ida in Iraq. It said the attacks were in response to "the conspiracy against the Sunnis whose blood and honour were shed by Crusaders and the Shiites". It was also "revenge for the Sunnis in Qaim", a reference to an offensive launched in that area by US and Iraqi government forces.

The "martyrdom lovers and heavenly yearners" had selected the three targeted hotels after "a month of surveillance and information gathering" and wore explosive belts "in order to achieve greater accuracy in hitting the target", the statement said. "Those who executed the plan were able to enter the sites after passing through all the security measures of which the descendants of the traitors [the Hashemite dynasty of King Abdullah II] were boasting".

Abu Khabib, described as the leader of the group, was said to have detonated his device at the Radisson SAS hotel, killing people at a wedding party. He was followed by Abu Maath at the Hyatt hotel where the victims included two senior Palestinian officials. Om Omaira "chose to accompany her husband [Abu Omaira] to his martyrdom". Their vehicle blew up at a police checkpoint outside the Days Inn hotel.

The statement by Zarqawi's group said the hotels had been targeted because they were supposedly used by "American and Israeli intelligence and western European governments" to launch a war on Islam.

Middle East observers say the detailed "justification" by al-Qa'ida in Iraq may have been in response to the fierce condemnation of the attacks across the Arab world. There were also demonstrations for the second day running in Amman to show solidarity against the bombings, and Islamic groups called for rallies to follow mourning prayers in the mosques.

Police in Amman said most of those arrested were Iraqi or Jordanian. Jordan is home to an estimated 400,000 Iraqis who have left their country since the war. Most have made the move to escape the state of near anarchy in Iraq, but the government in Baghdad claims some are actively helping the insurgents.

Kofi Annan, the United Nations secretary general, said during a visit to Jordan yesterday: "No ideology can justify the killing of innocent people." Condoleezza Rice, the US Secretary of State, insisted, during a brief visit to Iraq, that the security situation in the country was getting better.