Eruptions at Italy's Mount Etna and the smaller Stromboli volcano spewed hot ash and lava, raising alert levels on the Mediterranean island of Sicily and forcing a temporary shutdown of Catania Airport on Friday.

Etna, one of the world's most active volcanoes, has seen intense activity in recent days, lighting up the sky near the city of Catania, while Stromboli off the northern Sicilian coast has spilled lava into the sea.

Italy's civil protection agency issued its top, red alert for Stromboli, warning the situation could deteriorate.

Civil Protection Minister Nello Musumeci said Stromboli was "under surveillance", adding that authorities were making sure evacuation plans were ready in case of emergency.

The fire brigade said they had preemptively doubled the number of firefighters on the island.

Around Catania, on the eastern coast of Sicily, residents and authorities moved to clean up the city after streets and cars were left smothered in black volcanic ash, while the nearby airport was closed.

"The runway at Catania Airport is unusable due to the volcanic ash fall. Both arrivals and departures are suspended," the airport said in a statement, adding that operations were due to resume at 3:00 p.m. (1300 GMT).