"This is a terrible tragedy," White House spokesman Scott McClellan told reporters on Air Force One as President George W. Bush travelled to his Texas ranch.

"Our thoughts and prayers are with those who were injured and with the families of those who were killed. And we are offering humanitarian assistance."

McClellan said exact details of the US contribution to a state Bush has branded part of an "axis of evil" would be announced later.

"We all come together behind the Iranian people at a time like this to assist those who have been injured and those families who have been impacted by this terrible tragedy," he said.

Between 5,000 and 6,000 people were killed when the earthquake destroyed the historic centre of Iran's southeastern fort city of Bam on Friday and another 30,000 were hurt, officials and state media said.

TERRA.WIRE