A United Airlines flight from Chicago to Hong Kong was diverted to Alaska after the flight crew reported a man on board had vandalised two airplane lavatories by spreading human waste, airport police said on Friday.

"We received a report of a passenger who had messed up the bathrooms with his own faeces," Anchorage Airport Police Lieutenant Joe Gamache said.

The man, a 22-year-old Vietnamese passport holder with U.S. residency, was escorted off the plane in handcuffs on Thursday night and met by law enforcement in the terminal, Gamache said.

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The flight, destined for Hong Kong, was diverted to Alaska after the incident. Photo: Stock/Getty

After being interviewed by authorities through a translator, he was transported to an Anchorage hospital for a mental evaluation.

The man made no threats and did not try to interfere with the flight crew, Gamache said, adding that no charges have been filed.

United Airlines, owned by United Continental Holdings Inc, said there were 245 people on board the plane and said it provided hotel accommodations for its customers.

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The man was escorted off the plane in handcuffs. Photo: Stock/Getty