A group in Iraq, led by Jordanian militant Abu Musab al-Zarqawi, has pledged allegiance to Osama bin Laden.
It said it was in contact with al-Qaeda over operations in Iraq, according to an Internet statement posted today.
Washington says Zarqawi is al-Qaeda's link to Iraq but the statement was the first to announce an allegiance to bin Laden's group.
Meanwhile, heavy fighting has been continuing between US forces and insurgents in the Iraqi rebel stronghold of Fallujah.
US warplanes have attacked targets in the city and tanks have fired at positions on its eastern edge.
The rebels responded with mortar rounds and rocket-propelled grenades.
Hospital officials said there had been casualties from the air strikes but heavy fighting had prevented ambulances from reaching them.
Overnight air raids are reported to have killed three people and wounded five others.
Iraq's interim government warned last week of a major offensive against Fallujah unless its residents handed over al-Zarqawi and his followers.
Elsewhere in Iraq, the US military are investigating the cause of a double helicopter crash which occurred last night in the capital, Baghdad.
Two US soldiers were killed in the crash and others were injured.
