An audio message purportedly from the head of al-Qaeda in Iraq, Abu Musab al-Zarqawi, says the Jordan bombings were not meant to hit a Muslim wedding.
The US has placed a $25m bounty on Zarqawi's head
The voice in the tape defends the triple hotel bombings in Amman, saying the group had meant to target US and Israeli intelligence agents.
The 9 November blasts killed 54 people, and caused widespread public outrage.
At least 100,000 people marched through Amman on Friday in the latest mass show of anger at the suicide attacks.
"Zarqawi, you coward, what brought you here?" shouted the marchers.
The two-hour march concluded with a rally in central Amman, where dignitaries and clergymen addressed the crowd, condemning Jordanian-born Zarqawi and his group.
Before the attacks, Zarqawi appeared to enjoy a certain sympathy in some sections of Jordanian opinion, the BBC's Jim Muir says.
But the death of so many Jordanian civilians seems to have eroded that sympathy very sharply, our correspondent says, and this broadcast seems to be aimed at regaining that lost ground.
In the audio message, which was posted on a website often used by insurgents in Iraq, the speaker says his group had meant to target a meeting of US and Israeli intelligence officials.
He says the deaths of the wedding party guests in one of the hotels was due to a roof collapsing.
Security has been stepped up during the rally in Amman
"We ask God to have mercy on the Muslims, who we did not intend to target, even if they were in hotels which are centres of immorality," the speaker says.
Warning of further attacks in the country, the speaker tells Jordanians to avoid going near large hotels, military sites used by US forces and embassies of the countries that took part in the Iraq invasion in 2003.
The speaker also threatens to kill Jordan's King Abdullah.
Al-Qaeda in Iraq had already claimed responsibility for the blasts in Days Inn Hotel, the Radisson SAS and the Grand Hyatt.
The Jordanian authorities have named three Iraqi suicide bombers, as well as an alleged fourth bomber who failed to blow herself up.
The Iraqi woman, Sajida Mubarak Atrous al-Rishawi, was shown on TV last weekend making an apparent confession.
In her statement, she said her and her husband took up positions in opposite corners of a wedding hall and she fled with the survivors when her charge failed.