The Boeing 747 freighter took off in South Africa, some 11 hours away by air, and stopped en route in Nairobi, Kenya, according to flight data.

"The man is doing well considering the circumstances and has been taken to a hospital," said the police - who are responsible for Dutch border control - in a statement.

Royal Dutch military police said the man's age and nationality had not yet been determined.

'Very unusual'

"Our first concern, of course, was for his health," said spokeswoman Joanna Helmonds.

"This is definitely very unusual that someone was able to survive the cold at such a height - very, very unusual."

A spokesperson for freight carrier Cargolux confirmed in an email that the stowaway had been on a flight operated by Cargolux Italia.

"We are not in a position to make any further comment until the authorities and the airline have completed their investigation," they said.

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A spokesperson for Amsterdam's Schipol Airport declined to answer questions about the incident.