A Turkish Airlines flight carrying more than 250 people en route to Brazil was forced to change course and land in Casablanca today after a bomb threat, the airline's second scare in two days.

Flight TK15 had departed from Istanbul and was headed for Sao Paulo when a note with the word "bomb" was found in the lavatory, a spokeswoman said.

The plane declared an emergency and diverted to the North African city, she said. The Boeing 777 with 256 passengers on board landed at around 2.30pm.

On Sunday, a Turkish Airlines flight from Istanbul bound for Tokyo turned back shortly after take-off when a note reading "C4 Cargo" was found on the lavatory door, Turkish media said.

No explosives were found on that aircraft.

The Brazil-bound aircraft was due to resume its flight once it was deemed safe, the spokeswoman said.

Moroccan aviation authorities said Casablanca airport was operating normally after the landing, and the aircraft was undergoing the normal procedures for such an incident.

Officials for Brazil's aviation authority and the private airport operator in Sao Paulo had no additional information.