Three explosions hit hotels in Jordan's capital Wednesday night, killing at least 57 people and wounding more than 300 others in a coordinated terrorist attack, Jordanian officials said.

Deputy Prime Minister Marwan Muasher confirmed that the downtown Amman attacks were carried out by at least three individuals: a homicide bomber who walked into a wedding at the Radisson SAS, another homicide bomber who walked into the lobby of the Grand Hyatt and a homicide car bomber who tried to drive into the Days Inn.

Jordanian King Abdullah II, who in a statement described the blasts as "criminal acts perpetrated by a misled and misleading group," cut short his official visit to Kazakhstan to return home.

The king affirmed in his statement that such terrorist operations "would not dissuade Jordan from pursuing its role in fighting terrorism and the criminal terrorist groups and those who are behind them and justify their acts" and vowed that the terrorists will be brought to justice.

A U.S. military official said so far no Americans were counted among the dead. Jordan is an important Middle East ally of the United States, and the U.S. Embassy is three miles from the blast site.

"I've just been apprised of them and we are watching the situation, but clearly this is a great tragedy," said Secretary of State Condoleezza Rice. "Again it shows that people will take innocent life without any remorse, and it just shows the very difficult war that we're fighting."

The White House offered its assistance in a statement: "Jordan is a close friend of the United States, and we will offer every possible form of cooperation in investigating these attacks and assisting in efforts to bring these terrorists to justice."

One U.S. counterterrorism official confirmed that the CIA and the National Counterterrorism Center were monitoring the situation. An FBI spokesman told FOX News that if a request for help came in, U.S. agents would go to Jordan. The spokesman said the FBI has people "ready to go" if such a request comes through the State Department.

Jordan closed all its borders within hours as a manhunt began. All ministries, government departments and public institutions in Jordan were to close on Thursday, Prime Minister Adnan Badran said in a statement.

Jordan's news agency reported that dozens were expected at organized marches in Amman and elsewhere Thursday to protest the attacks.

Jordanian police said the three hotel blasts indicated the involvement of Al Qaeda, which has launched coordinated attacks on high-profile, Western targets in the past. And the date of the attack, Nov. 9, is noted in many other parts of the world as 9-11.

Muasher said Abu Musab al-Zarqawi, the Jordanian-born leader of terrorist group Al Qaeda in Iraq, was a top suspect.

One U.S. counterterrorism official added that Jordan is also an ally of Israel, and a Palestinian terrorist group like Hamas could be responsible. The official also said that a preliminary investigation did not show the explosives used to be very sophisticated, widening the scope of possible suspects to less-organized groups sympathetic to Al Qaeda.

Iraq Violence Spilling Over?

FOX News producers in Amman at the time of the first blast — which occurred at 8:50 p.m. local time — said the attack was aimed at a "triangle" of three hotels in the city. A FOX News producer who was inside the Grand Hyatt when it was hit reported feeling the shockwaves from the blast, and said he and everyone else in the hotel were quickly evacuated. The blast from the homicide bomber completely shattered the hotel's stone entrance.

The attack on the wedding at the Radisson appeared to have resulted in the most casualties. About 300 people were celebrating there when the bomber walked in and detonated.

The hotel is popular with American and Israeli tourists and was the target of a plot in 2000. Israel's ambassador to Jordan, Yaakov Hadas, told Israel TV from Amman there were no reports of Israeli casualties.

"We thought it was fireworks for the wedding but I saw people falling to the ground," said Ahmed, a wedding guest who did not give his surname. "I saw blood. There were people killed. It was ugly."

The fewest casualties may have occurred at the Days Inn, where the homicide bomber was unable to crack the concrete security barriers surrounding the hotel before detonating.

Downtown Amman is frequented by wealthy Jordanians and international travelers, including diplomats, military personnel and other high-ranking officials. A constitutional monarchy, Jordan is seen as one of the most secure and open countries in the volatile Middle East.

Jordan's rulers, King Abdullah II and Queen Rania, are cosmopolitan, modern and friendly to the West. Women have many rights in Jordan their neighboring counterparts do not. Both are also noted for their humanitarian work, in particular helping the impoverished of their kingdom.

But those qualities have made Jordan a target of ire among terrorists in the region.

Terrorism analyst Steve Emerson told FOX News that in the past five years, there have been at least a dozen plots against American-dominated hotels in Amman, "all of which have been successfully stopped."

But terrorists, specifically Al Qaeda, "strike the soft underbelly where American security … operations are not as extensive," Emerson said. "They find out the soft target and this is the quintessential soft target, that is, where there's very little protection."

But Jordan boasts of the best intelligence services in the world — which may mean the attacks should alarm America and its allies.

"Jordan is one of the spymasters of the Middle East. Their intelligence service is one the best," former CIA official Michael Swetnam told FOX News, noting that Jordan has been of great assistance in American efforts to scrub the world of Al Qaeda.

"But about the only part of Al Qaeda that neither they nor we have a great intelligence handle on is Zarqawi's network in Iraq," he added. "About the only people who could pull this off relatively easily would be Zarqawi's network out of Iraq, because they're just not well infiltrated by any of us."

If Zarqawi's network is indeed responsible for the attack, the United States may feel compelled to get involved.

"I think we all expected that Jordan was going to be a target very, very soon," added Global Options CEO and terrorism analyst Neil Livingstone, noting that there has been news recently of more Jordanian cooperation with the United States in the War on Terror. "This is something, it was only a matter of time, before they [Zarqawi's group] tried to destabilize the Jordanian regime."

He added: "This is probably an organized effort to undermine the Jordanian government and kill Americans in the balance. ... The United States has been putting more and more pressure on the insurgents in Iraq ... I think this is probably an effort by Al Qaeda to say 'we want to open a new front.'"

Said Swetnam: "We shouldn't lull ourselves into believing they won't come here in the near future."

But the attacks may not have the intended effect on Jordan, others observed.

"Knowing Jordan as well as I think I do in this case, I think this is going to be very counterproductive [for the terrorists] in Jordan. Sure it will scare everybody but it's not going to convince them the Usama bin Laden cause is a good one, by any means, I think it will turn them against him," Lawrence Eagleburger, the secretary of state under President George H.W. Bush, told FOX News.

Even though many residents of Jordan are Palestinian, Eagleburger said he doesn't believe Al Qaeda attacks in that country will help radicalize the population, either.

"It might do that in some other countries in the region but I think in Jordan it will decrease whatever population this [Al Qaeda] bunch had … if the attackers care at all about the impact on Jordan, I think they've made a mistake," he said.

No Stranger to Terror

Last August, three Katyusha rockets were fired in the port city of Aqaba, but missed two docked U.S. Navy vessels, their intended targets. But one Jordanian soldier was killed and another wounded in the suspected terrorist attack. Al Qaeda in Iraq claimed responsibility for that attack, as did the Abdullah Azzam Brigades.

In 2002, USAID official Lawrence Foley was gunned down in front of his home in Jordan. Five men, including Al-Zarqawi, were convicted of participation in the killing in April 2004. Al-Zarqawi was convicted in absentia, and is now Iraq's most wanted terrorist as the leader of Al Qaeda in Iraq, the group that's been blamed for a rash of kidnappings, killings and attacks against U.S. forces in Iraq.

In 2000, Al-Zarqawi was convicted in absentia for planning Al Qaeda attacks against the Radisson SAS and other Western targets. U.S. officials believe al-Zarqawi and bin Laden operations chief Abu Zubaydah were chief organizers of that foiled plot.

The attack was to take place during millennium celebrations, but Jordanian authorities stopped it in late 1999. Abu Zubaydah was captured in March 2002 in Faisalabad, Pakistan, in a raid by the CIA, FBI and Pakistani authorities.

In July, prosecutors indicted five Jordanians in an alleged conspiracy to attack intelligence agents, tourists and hotels in Amman. Al Zarqawi has not been linked to the alleged plot.

Livingstone said it shouldn't take long for investigators to conclude Al Qaeda or some indigenous offshoot of the terror network, is to blame for Wednesday's attacks. Noting that every explosive has a signature fingerprint, he said investigators will also compare the bomb remains found in the Amman attacks to those used in previous bombings, as well as study the surveillance tapes from the hotels to track down the bombers.

"This is not going to be, I think, a very difficult investigation, I think we're going to have answers soon," Livingstone said.

U.S. officials said a letter dated July 9 to Zarqawi from Al Qaeda deputy leader Ayman al-Zawahiri, acquired during American operations in Iraq, recommends a four-stage expansion of the war in Iraq that would take the fighting to neighboring Muslim countries.

Raw Data: Text of Zawahiri Letter (pdf)

"It has always been my belief that the victory of Islam will never take place until a Muslim state is established ... in the heart of the Islamic world," al-Zawahiri wrote in the letter, which an Al Qaeda-related Web site has claimed is a fake.

The letter laid out his long-term plan: the expulsion of American troops from Iraq, the establishment an Islamic authority and the expansion of the war to Iraq's secular neighbors, including Lebanon, Jordan and Syria.

The last major terror attack blamed on Islamic militants was the July 7 bombings of the London transit system that killed 56 people, including four bombers. The most recent major attack concretely linked to Al Qaeda was the Madrid subway bombings that killed 191 people on March 11, 2004.

FOX News' Jennifer Griffin, Catherine Herridge, Liza Porteus, Jane Roh, Serene Sabbagh and The Associated Press contributed to this report.