LOS ANGELES, Sept. 1 -- Mel Gibson has apologised after footage of him appearing to mock an American Sign Language (ALS) interpreter during a fan convention sparked criticism online.

The 70-year-old actor described his behaviour at Fan Expo Canada as "thoughtless idiocy", while insisting he had not intended to cause offence.

"Sometimes when you get pushed out on a stage in a spotlight your mind is all over the place," Gibson said in a statement to The New York Times.

He added that there had been no "intended maliciousness" behind the incident, saying: "I certainly apologise to anyone who was upset by it."

The controversy erupted after Gibson appeared at Fan Expo Canada in Toronto on August 29 for a question-and-answer session about hi...