The statement, allegedly coming from Jordanian-born Abu Musab al-Zarqawi's group al-Qaida in Iraq, was posted on the internet but could not be verified.
It read: "The group charged with planning, preparing and implementing was made up of three men: commanders Abu Khabib, Abu Muaz and Abu Omaira. Their fourth was the venerable sister Om Omaira."
The Jordanian authorities say they have found the remains of three bombers and are piecing the bodies together for identification purposes and taking DNA samples.
The claim came as mosques across Jordan were holding mourning prayers on Friday for the victims of the attacks.
UN Secretary-General Kofi Annan arrived in the capital, Amman, as the Jordanian authorities continued to investigate Wednesday night's blasts that killed at least 57 people, including 12 foreigners, and wounded more than 100.
Candlelit vigils were held at the hotels, the Grand Hyatt, Radisson SAS and Days Inn, while a clear up operation continued.
Meanwhile Iraq's Oil Ministry revealed that three of its experts had died in the blasts and a fourth had been wounded. The experts were used to travelling to Amman as many foreign contractors refuse to visit Iraq for security reasons.
Police said they had arrested at least 120 people, mainly Iraqis and Jordanians, in a nationwide manhunt.
A senior police official had no details on the possible role of any of those detained. "Scores have been rounded up in different parts of the country since the attacks," he said. "Many may simply be innocent."
The four Palestinian officials with
the national flag draped over
There has been intense speculation in Jordan that Iraqi fighters were behind the attacks. Al-Zarqawi is said to have trained a special corps of at least 100 Iraqi bombers to conduct attacks inside, and possibly outside, Iraq.
At least one of the three bombers spoke to people inside the lobby of the Hyatt Hotel with an Iraqi accent before blowing himself up.
In figures released on Friday, Jordanian officials said the dead included 38 Jordanians, many of Palestinian descent; four Iraqis; an Israeli-Arab; four Palestinians; three Chinese; a Qatari and one Lebanese. Several bodies have not yet been identified.
The US embassy said late on Thursday that two Americans had died in the attacks and four had been wounded. It was not immediately clear if that number included the filmmaker Mustapha Akkad and his daughter Rima.
Jordan's King Abdullah II had promised to hunt down those behind the triple hotel bombings, claimed by Jordan-born Abu Musab al-Zarqawi's branch of al-Qaida, saying he will not allow the country's policies to be dictated by terrorists.
"We will pursue those criminals and those who are behind them and we will reach them wherever they are," he said in a televised address to the nation on Thursday.
"We will pull them from their holes and bring them to justice," the king said, without mentioning specific measures.
Aljazeera reported that a convoy carrying the bodies of four officials from the Palestinian Authority killed in the explosions arrived in Ram Allah on Friday.
The bodies of one of the
Palestinians is handed to the PA
The convoy passed a crossing in Rafah before heading to Ram Allah and was received by a number of Palestinian Authority officials.
Palestinian flags have been flown at half mast in mourning over the 27 Palestinians killed in the explosions including two senior security officials and the commercial attaché in the Palestinian embassy in Cairo.
In his address, the Jordanian monarch said Jordan was not afraid and would not be "blackmailed" by the bombers.
"We will confront these cowardly terrorist groups that have
no religion or conscience," he said.
"These acts will not make us change our positions and convictions," he said, nor would they force Amman "to retreat from our role in fighting terror in all its forms."
Most of the casualties were Jordanian nationals.
Earlier, the Jordanian authorities announced they had arrested several people in connection with the bombings.
Jordan's Queen Rania visited the
injured at an Amman hospital
"A number of suspects were arrested and a number of cars were seized in connection with the terrorist attacks," a Jordanian security official told the country's state-run Petra news agency.
"The investigation with the suspects is under way," the unnamed source added, without revealing the exact number or identities of those arrested.
Another Jordanian security source told AFP on Thursday that six vehicles were seized by the authorities soon after the attacks "including two that have Iraqi licence plates".
Jordan's public security department has asked photographers who were at the scenes of the attacks to hand in any film they had taken that might be of use to the investigation.
Police have reiterated that they had no advance warning an attack was imminent.
Police have appealed to the public
for film of the blast sites
Deputy Prime Minister Marwan Muasher said two bombers attacked the Grand Hyatt and the nearby Radisson SAS.
The Days Inn attack was carried out by an explosives-laden vehicle that blew up outside the hotel after failing to cross a police line.
The casualty figures show the dead included at least 15 Jordanians, five Iraqi nationals, three Chinese, a Saudi, a Syrian, a Palestinian and an Indonesian, while the bodies of 30 people had yet to be identified.
Israel radio reported that an Israeli businessman was among the dead.
In an internet statement released on Thursday, al-Qaida in Iraq said it had carried out the bomb attacks.
"A group of our best lions launched a new attack on some dens..."
Al-Qaida in Iraq internet statement
"A group of our best lions launched a new attack on some dens... After casing the targets, some hotels were chosen which the Jordanian despot turned into a backyard for the enemies of the faith, the Jews and Crusaders," the statement on a website usually used by the group, said on Thursday.
"Let the tyrant of Amman know that his protection ... for the Jews has become a target for the mujahidin and their attacks, and let him expect the worst," it added.
In a separate development, al-Qaida in Iraq also claimed responsibility for Thursday's bombing of a restaurant in Baghdad which killed 31 people, according to a statement posted on the internet.
According to the Associated Press, the first explosion occurred at 8.50pm (1850 GMT) in or near the lobby of the Grand Hyatt.
An al-Qaida-linked Iraqi group
has claimed responsibility
A second blast followed shortly afterwards at the Radisson.
The third blast hit a nightclub at the Days Inn.
Most of the victims at the Radisson were Jordanians attending a wedding banquet in a ground-floor reception hall, where a man strapped with explosives infiltrated the crowd.
"We thought it was fireworks for the wedding; but I saw people falling to the ground," said Ahmad, a wedding guest who did not give his surname. "I saw blood. There were people killed. It was ugly."
Following Wednesday's explosions, security was beefed up across the Jordanian capital, especially around hotels and diplomatic missions.
In Iraq, government spokesman Laith Kubba condemned the bombings, saying they showed that countries in the region had to stand together in the fight against terrorism.