Residents were urged to follow the instructions of the local civil defence authorities on the small volcanic island north of Sicily.
The National Institute of Geophysics and Volcanology (INGV) said increased volcanic activity had been detected at Mount Stromboli.
Lava and ash had poured out of the volcano and into the sea, INGV said.
Only a few hundred people normally live on Stromboli island.
Many tourists travel there by sea from the mainland or from Sicily to climb the volcano, which is about 920 metres high and erupts regularly.
Almost 200km away an orange alert was put in place on the much larger island of Sicily, where Mount Etna has also been active.
A shower of ash fell on the nearby city of Catania, causing the airport there to close for take-offs and landings for several hours.
Grey-black dust was also deposited in the streets and on houses in other towns.
Etna continued to spew fountains of lava overnight.
At times, there was a cloud above the volcano that reached almost 5km into the atmosphere.
The IGNV said that Etna then slowly calmed down.
Etna, which is about 3350 metres high, is Europe's largest active volcano.
Its exact height is constantly changing due to eruptions and the build up of cinders and lava.
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