Harry Potter star Emma Watson was forced to flee her university residence in her pyjamas after a fire scare.

Students at the top US college where the actress is taking an English Literature degree were evacuated from dorms.

Emma, 20, voted Britain's best-dressed woman, stood outside in nightclothes as the fire alarm blared.

The panic in the early hours ended when "smoke" was found to be steam from a faulty pipe at Brown University in Rhode Island, the Sun reports.