Three senior figures in the Palestinian administration were among at least 56 people killed in suicide bomb attacks on three luxury hotels in Jordan, it was confirmed today.

Al-Qaeda in Iraq, the terror group led by Jordanian-born Abu Musab al-Zarqawi, posted a statement on a website claiming responsibility for the three synchronised blasts which ripped through the Grand Hyatt, Radisson SAS and Days Inn in Amman, the capital of Jordan.

Two suicide bombers, with explosives strapped to their bodies, struck at the Radisson and Grand Hyatt. The third attack was apparently a car bomb.

Several arrests have been made this morning connection with the attacks in which 300 people were injured. Land borders were reopened after being closed for nearly 12 hours.

A wedding party was under way at the Radisson when the first bomb went off at 9pm local time. The fathers of the bride and groom were the five guests killed. "We thought it was fireworks for wedding ... then I saw blood," said one guest.

Jack Straw, the Foreign Secretary, stopped off briefly in Amman to survey the carnage and offer a pledge of British support for Jordan, which has until now been spared major bloodshed, despite being one of Washington's closest allies in the Middle East.

"Jordan's sorrow is our sorrow. Jordan's grief is our grief. Jordan's determination to fight this mindless terrorism is our determination as well," Mr Straw said during a brief press conference on the steps on the Hyatt.

Amman - a comfortable, hilly city of white stone villas and glitzy high-rises - had largely avoided attacks and had earned a repuutation as an oasis of fragile stability in the region beset by turmoil.

Most of those killed in the blasts at the hotels which are popular with travelling Western diplomats, contract workers and businessmen were guests at the wedding banquet.

Other victims included three Chinese, all from China’s elite training university, who were visiting the desert kingdom, and a senior Palestinian banker. Hossam Fathi Mahajna, 40, an Arab-Israeli businessman was also named as being among the dead.

An American businessman told the Associated Press news agency: "Several of my friends have died. The people who carried this out were cowards."

A series of demonstrations sprang up around the kingdom as Jordanians, many carrying photographs of King Abdullah II, took to the streets to protest against the blasts. The King supported the US operation in Iraq against the wishes of his five million subjects.

Flags flew at half mast on government buildings across the West Bank and Gaza Strip as three days of mourning were declared. The administration publicly denounced the killings as a crime against humanity and Arab security.

Bashir Nafeh, director of military intelligence chief in the West Bank, was named as being among the dead. He had stopped in Amman with Colonel Abed Allun, a high-ranking security official, and Rawhi Futtah, the commercial attache at the Palestinian Embassy in Egypt and brother of the speaker in the Palestinian parliament. All three were staying in the Grand Hyatt.

Ahmed Qureia, the Prime Minister of the Palestinian Authority, described Mr Nafeh as a martyr. "It is a sad day for Palestine as for Jordan and all peace lovers in the world," he said.

Laith Kubba, a spokesman for the Iraqi Government, said that the attack should alert Jordan that it needed to stop playing host to former members of Saddam Hussein’s regime.

"I hope that these attacks will wake up the ‘Jordanian street’ to end their sympathy with Saddam’s remnants ... who exploit the freedom in this country to have a safe shelter to plot their criminal acts against Iraqis," he said.

In an unauthenticated statement posted on an Islamic website used by militant groups, a spokesman claiming to represent al-Qaeda in Iraq said that the three hotels had become "the back garden for the enemy of religion: Jews and crusaders."

Al-Zarqawi has long wanted to export his brand of Jihad to his homeland of Jordan, which he regards as a puppet kingdom in the service of America. He was blamed for the attack even before rescue workers had arrived on the scene.

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