A US air marshal has shot a man claiming to have a bomb on an American Airlines plane at Miami International Airport.

The man was shot on the runway linking the plane to the terminal at the airport.

The plane had just arrived from the Colombian city of Medellin.

Police and SWAT intervention teams immediately surrounded the flight at the airport.

"We can confirm that shots were fired on that flight," Miami police spokeswoman Mary Walters said.

But police gave no details of casualties or who had fired the shots.

US television networks quoted officials as saying the passenger had bragged about having a bomb and was shot as he put a hand into a bag.