AMMAN, Jordan -- Three almost simultaneous bomb explosions blasts tore through hotels in this capital last night, killing more than 50 people, wounding 150, and sending fear and panic through the streets of the normally tranquil city.
Jordanian authorities immediately shut down many of the capital's main roads and deployed dozens of ambulances, police cars, and military vehicles to help evacuate the wounded to a half-dozen overflowing hospitals.
The country's land borders were closed about an hour after the attacks.
No group asserted responsibility for the attack, though several government officials said the coordination and execution, apparently by suicide attackers, bore the mark of the Al Qaeda network.
The explosions were set off in rapid succession at about 9 p.m. Hours afterward, central Amman streets were filled with hundreds of people. Some were hotel guests who said they did not know where to go; others were family members of victims, wandering from hospital to hospital looking for information about their loved ones.
''I carried at least 20 people back and forth to the Jordan Hospital. Everybody was screaming and crying, mothers were confused. . . . I was just shocked," said Marwan Muhammed Hani, 22, a taxi driver.
Hani had parked his vehicle at the Grand Hyatt hotel when a bomb exploded inside.
Each of the blasts targeted a hotel owned by a US-based chain. The first bomb killed more than 20 people in the Grand Hyatt, one of the city's largest lodgings, police at the scene said.
At the Radisson SAS Hotel, at least 20 were killed at a wedding reception in a banquet room, according to police and hospital officials.
Initial reports suggested that suicide bombers on foot were responsible for those two blasts, although police at the scene said a rigged device had been planted in at least one of the hotels.
The third blast resulted from a car that was detonated in the street outside the Days Inn, police and government officials said.
The death toll was the largest in a hotel bombing since July 23, when attacks on three hotels in the Egyptian resort of Sharm el-Sheikh killed up to 88 people.
''We still don't know why this was done. Obviously anyone who blows himself up in a wedding hall is not someone who wants the good of his country or the good of any human being," Jordan's deputy prime minister, Marwan Muasher, said to reporters in front of the Radisson.
He said that there were 57 deaths as of 11:30 p.m. and that it appeared that most of the victims were Jordanians.
''We thought it was fireworks for the wedding, but I saw people falling to the ground," said Ahmed, a wedding guest at the five-star Radisson who did not give his family name. ''I saw blood. There were people killed. It was ugly."
Despite its proximity to Iraq, Amman is widely considered one of the Middle East's safest capitals, and luxury hotels have had only minimal apparent security. Drivers could bring cars directly to the front doors of most hotels, and no metal detectors or identification checkpoints were present.
Hours after the attacks last night, however, police closed streets in front of several large hotels and employees checked room keys and waved metal-detecting wands at people entering.
''Things here had gotten very relaxed and soft. No one seemed to care about security procedures," Jamil Nimri, a Jordanian newspaper columnist, said while looking at the wreckage of the Radisson.
Amman has become a base for Westerners who fly in and out of neighboring Iraq for work. The city's main luxury hotels downtown are often full of US and British officials and contractors.
''Obviously this is something Jordan is not used to," Muasher told the CNN network. ''We have been lucky so far in avoiding those incidents." He said that most of those who died or were wounded appeared to have been Jordanians, and that authorities had sealed the country's land borders.
A State Department official said there was no information on any American casualties. A Jordanian security official, speaking on condition of anonymity because he had not been authorized to address the media, said the dead included at least three Asians.
Jordanian forces have thwarted a number of attacks in recent years. In what is known as the millennium plot, Abu Musab al-Zarqawi, the Jordanian who is now the most wanted insurgent leader in Iraq, targeted several tourist sites in the city, including the Radisson, just before New Year's Eve in 1999.
Authorities uncovered the plot, and Zarqawi fled the country.
In April 2004, Jordanian officials said they had broken up an attempted chemical attack on the capital that they said could have killed 20,000 people. Police said they also thwarted another planned attack against hotels and embassies in the summer of 2004.
In August of this year, Zarqawi's Iraq branch of Al Qaeda asserted that some of its fighters had launched Katyusha rockets that had narrowly missed a US warship in the Red Sea port of Aqaba, also in Jordan.
''All the fingers for what happened tonight point to Al Qaeda and Zarqawi," said Muhammed Arsalan, assistant to the country's parliament speaker, who toured each of the bomb sites.
''They have been trying for a long time, and we were lucky. But they found a weak point," Arsalan said.
In February, US intelligence indicated that Osama bin Laden was in contact with Zarqawi, enlisting him to conduct attacks outside of Iraq, said another US counterterrorism official, who also spoke on condition of anonymity. Jordan has arrested scores of Islamic militants on charges of plotting to carry out attacks, and has sentenced many militants to death in absentia, including Zarqawi.
Jordanian officials declared that today would be a national day of mourning. King Abdullah said on national television that ''the hand of justice will reach the perpetrators wherever they are."
President Bush said in a statement: ''The barbaric acts again demonstrated the terrible cruelty of the terrorists and the great toll they take on civilized society."
''To the people of Jordan and King Abdullah, we pledge our full support in their efforts to bring the terrorists to justice," he added.
Hotel employees sounded an alarm just after the explosion at the Grand Hyatt, which guests said took place in a ground-floor bar. Guests said they were first directed to a basement shelter, and then were handed white blankets and asked to leave the building through emergency exits.
Usama Jabr, 59, an Iraqi physician, said he was visiting Amman for a cardiothoracic convention, and was hoping for some ''peace and quiet." He was in the Grand Hyatt's restaurant with some colleagues ''when we heard something that sounded like a rocket attack I heard once in Baghdad," he said. ''It was a violent explosion. We saw smoke and broken glass, and everyone started to panic. There was a waiter crying and yelling because of cuts in his eyes."
At the Jordan Hospital, family members of the victims gathered outside and grew increasingly agitated as police barricaded the doors and would not let anyone enter. Twice, wailing women broke through the police lines and charged toward the door, only to be turned away by hospital staff.
A man speaking on a cell phone fell to his knees and began to shout, ''No, no, no!" Friends helped him to his feet and led him to a waiting car.
Ahmed Zerkia, 35, punched the keys of his cellular phone with trembling fingers. His brother Aref, 50, had been in the wedding party, he said, with dozens of other family members.
''My cousin called me and said, `Your brother is dead.' But I want to know for sure, so I came here," said Zerkia, his eyes welling with tears. ''He's my big brother. He's like my father. I try and try but I cannot reach anyone in his family."
Material from the Associated Press was used in this report.