The state-run KUNA news agency said the plane from the Omani city of Salalah bound for Cologne landed there Sunday morning over the threat, AP reported.
Some 299 people were evacuated from the plane and authorities were searching the flight.
The only plane that took off from Salalah bound for Cologne on Sunday morning was Eurowings flight No. EW117, an Airbus A330-203.
Eurowings did not immediately respond to a request for comment.