Amman : Suspected suicide bombers blew themselves up at three international hotels in Jordan's capital Amman, killing 57 people and wounding 110 others.

In Wednesday's apparently synchronised attacks, two bombs exploded while crowds were celebrating weddings, leaving blood and destruction at Amman's luxury Grand Hyatt hotel and the nearby Radisson SAS. A third blast targeted a Days Inn hotel.

There was no immediate claim of responsibility, but counter-terrorism officials pointed the finger at Al Qaida and its leader in Iraq, Jordanian Abu Musab Al Zarqawi, because of the simultaneous attacks - a hallmark of the militant network.

"The initial investigations so far show that the blasts that caused the deaths of 57 people and wounded 110 people had been executed by explosive devices and suicide bombings," said a statement issued by the Jordanian cabinet.

King Abdullah II - who cut short an official visit to Kazakhstan and was returning home Wednesday night - condemned the attacks.

"The hand of justice will get to the criminals who targeted innocent secure civilians with their cowardly acts," he said in a statement carried by the official Petra news agency.

He blamed a "deviant and misled group" for the attacks. "The attacks targeted and killed innocent Jordanian civilians," the king said in a statement.

Deputy Prime Minister Marwan Al Muasher told a news conference most of the victims were Jordanians. Authorities said they did not yet have any details on all the nationalities.

Muasher said there was no claim of responsibility but that Al Zarqawi was a "prime suspect."

Prime Minister Adnan Badran declared Thursday a national holiday - apparently in order to allow tightened security measures to take hold.

The explosion at the Radisson tore through a banqueting room where about 250 people were attending a wedding reception, witnesses said. A smaller wedding, attracting several dozen well-dressed young people, was going on at the Hyatt.

A security official said the dead included at least three Asians, possibly Chinese. He said the injured were of different nationalities, including Germans, a US citizen of Arab origin, Egyptians, Saudis and Iraqis.

Famed Syrian movie director Mustafa Aqad was among the injured and his daughter was killed, the official added.

The head of the Palestinian intelligence services, Bashir Nafeh, was among those killed in the blast that shook the Grand Hyatt hotel, a top Palestinian diplomat said on Thursday.

Initial police reports showed that the suicide bomber at the Grand Hyatt was possibly Iraqi, the official said. He said the middle-aged man, strapped with explosives under his Western-style suit, was stopped by suspicious security officials in the hotel's lobby.

Speaking in an Iraqi accent, the man said he was "looking around," and then blew himself up, the official added, saying hotel cameras had some shots of him.

Reporters at the Radisson and Hyatt saw dozens of wounded people, including one young woman hit by shrapnel in her legs and back and apparently left paralysed.

At the Hyatt, one waiter, identified by his name tag as Mustafa, lay motionless on the hotel's back steps as guests tried to resuscitate him before ambulance workers arrived.

Many Westerners, including tourists, businessmen and foreign contractors working in Iraq, were staying at the three hotels. The Radisson is known to be popular with Israeli tourists.

Police and some military units threw up roadblocks around hotels and embassies in the city, causing traffic chaos. Officials said Jordan had closed its borders.