"The investigation has arrived at the conclusion that al-Qaida was behind the attacks and specifically Abu Musab Al-Zarqawi's group," Deputy Prime Minister Marwan Muasher told a news conference on Saturday, adding that all three attackers were "non-Jordanian males".
The statement contradicts al-Qaida in Iraq which said four Iraqis - including a husband and a wife - carried out Wednesday's attacks against the Grand Hyatt, Radisson and Days Inn hotels that killed 57 people, including the bombers.
There was "no indication of a woman among the bodies of the perpetrators", Muasher said.
Muasher declined to comment on the precise nationality of the bombers but said they had entered Jordan from abroad.
The near simultaneous blasts against hotels frequented by Western security contractors and diplomats were among the worst attacks in Jordan's modern history.
Jordan, a close US ally and one of two Arab nations to have peace treaties with Israel, had been spared al-Qaida-linked attacks that have hit other countries in the troubled region, winning it a reputation for safety.
Al-Zarqawi is wanted in Jordan
for killing a US diplomat
Most of the victims were Jordanians attending wedding parties at the Grand Hyatt and Radisson hotels. Three Americans were killed in the attacks, a US embassy spokesman said.
Police have rounded up scores of people in a nationwide hunt for the attackers' accomplices, including Sunni extremist underground cells.
Suspicion about the attackers quickly fell on Iraqi Sunnis involved in fighting the Shia - and Kurd-dominated government in neighbouring Iraq.
Jordanian-born al-Zarqawi has been sentenced to death in Jordan for the 2002 murder of a US diplomat, while the United States accuses him of leading criminal operations in Iraq and has put a $25-million bounty on his head.
Once described as a "street thug" by King Abdullah II, al-Zarqawi was freed by the monarch in a general amnesty six years ago and has proved elusive despite the huge reward and the US hunt for him in Iraq.