A Boeing 777 operated by KLM has turned back towards Amsterdam's Schiphol International Airport after reporting an unspecified technical problem, the Dutch air traffic controller said on Sunday.

Flight KLM705, bound for Rio de Janeiro in Brazil, made a U-turn over Belgium after requesting a precautionary landing, an air traffic controller spokesman said.

It is not immediately clear what prompted this decision.

KLM said the safety of passengers and crew was never in danger, adding that another aircraft would be used to make the flight. (Anthony Deutsch; version française Jean Terzian)