“When the plane was taxiing, in the preliminary stages of approaching the runway, these people forced open a door and slid down the slides that were activated, and then they escaped,” the Alitalia spokesman told The Local.
The three Algerians had departed from Algiers and were due to fly to Istanbul after a layover in Rome, the spokesman said.
They are still missing. They were among a group of Algerians on the Alitalia AZ702 flight who had been denied entry to Italy, according to media reports.
The plane was immediately grounded for checks after the incident and police were called to the scene, Alitalia's spokesman said.
Italian border police were not immediately available for comment when contacted by The Local.
Rome's main airport is recovering from a fierce fire triggered by an electrical fault in a bar last week which partially destroyed a terminal and has led to many flight delays and cancellations.
By Catherine Hornby