Four people have been arrested after a 'fake bomb' made from cardboard with a small timer sparked a scare on an Air France flight, forcing its pilots to make an emergency landing in Kenya.

The four suspects were arrested were on board the Boeing 777 which was carrying 459 passengers and 14 crew members from Mauritius to Paris, CNN has reported.

Apparently passengers alerted cabin crew to the fake bomb inside a toilet. 

"After analysis it has been indicated that (the bomb scare) was a false alarm," Air France chief executive Frederic Gagey told a press conference in Paris.

He said that it appeared that the bomb scare was a "bad joke".

The 777 landed at Moi International airport in the Kenyan coastal city Mombasa. 

Gagey said there had been three bomb scares on Air France planes in the United States in the past 15 days.