Palma de Mallorca: Fleeing passengers shut down busy Spanish airport.

One of Spain's busiest airports shut down for nearly four hours on Friday after an apparent attempt by migrants to enter the country illegally.

A plane flying from Casablanca in Morocco to Istanbul, Turkey, was diverted to Palma de Mallorca after a medical emergency was reported aboard.

When the jet landed, 21 passengers ran off across the runways, reportedly escaping over the perimeter fence.

Police later made arrests but 12 were still on the run on Saturday.

Police are investigating whether the group's escape from the plane was spontaneous or an elaborate plot to immigrate illegally.

The top Spanish government official for the Balearic Islands, Aina Calvo, said the event was unprecedented for a Spanish airport.