Former US presidents Bill Clinton and George Bush alongside former British prime minister Tony Blair were forced to take shelter in the basement of a high school in Arkansas after a tornado warning.

The three former world leaders were attending a graduation ceremony at Little Rock's Central High School when the storm struck on Thursday night.

A spokesman for Mr Clinton said the three leaders took shelter downstairs, away from the assembled audience.

The powerful thunderstorm felled trees and power lines throughout Little Rock but no major damage or injuries were reported.

Later when the storm passed, the three leaders went to the Clinton Presidential Centre for a dinner.