However, officials say the activity is taking place at its summit and does not pose a risk to people.
“It could end soon or last for months,” said Eugenio Privitera, the director in Catania of Italy’s National Institute of Geophysics and Volcanology (INGV), speaking to Italian news agency ANSA.
He said the eruption does not pose risks to local people, but visitors to Etna will need to be kept away from the summit for their own safety.
The volcano previously erupted in late December 2018 and sparked earthquakes up to 4.8 magnitude that caused extensive damage to buildings in the vicinity.
Etna is also Europe’s biggest and highest volcano, reaching 3,330m metres at its summit, and has half a million years eruption history according to INGV, although not always in its current shape.
Its recent eruptions have typically been slow lava flows that pose no risk to the 900,000 people living in the surroundings and make for a spectacular sight at night.
As a result, Etna has become a popular tourist destination.
The lava flow descended to about 2,050 metres above sea level. But Italian news agency ANSA says the volcano’s activity has not yet caused problems for the nearby airport at the Sicilian city of Catania.