Three people died and nine were injured when a KTEL Intercity bus came off the road on the northeastern Aegean island of Hios on Monday morning.

A man and a woman, who have not been identified, were pronounced dead on arrival at the island's general hospital, while doctors were treating another nine passengers for injuries as firemen searched the site of the accident site for more possible victims.

The bus went off the road on its regular morning route between the villages of Kardamyli and Viki, when it crashed into a guard railing on the outskirts of Sikiada and tumbled down a gully, before catching fire.

Eyewitnesses told police that the bus careened out of control, entered the incoming traffic lane and crashed through the barrier. It rolled over at least three times down a gully as panicked passengers scrambled to get out of the vehicle before it burst into flames.

Rescue workers who arrived at the scene were unable to ascertain exactly how many passengers were on board the bus and whether any were missing, according to initial reports.

There was no information regarding why the driver lost control of the vehicle.