Mount Etna is Europe’s most active volcano. Located in Sicily, the 3,350m volcano’s eruption occured amid more than 130 earthquakes of up to 4.3 in magnitude. A blanket of volcanic ash also covered nearby villages, which ground planes to a halt at Catania airport temporarily.
Video footage from 2,500m (8,200 ft) up the volcano showed how quickly the ash spread.
People on the mountainside were immediately told to evacuate.
The Mount Etna observatory said lava also spewed from a new fracture near its south-eastern crater.
This was Etna’s “first flank eruption” in more than a decade, according to a local volcanologist.
Despite flights being halted after the eruption, Catania airport said lthe airspace had been reopened to allow four planes to land every hour later in the day.
Normal operations resumed at 8pm local time (7pm GMT).
Italy’s INGV volcanology institute said the eruption resulted in more than 130 earthquakes striking the surrounding area from 8.50pm (7.50pm GMT).
The biggest tremor was magnitude 4, which took place on the north-east side of Etna near Piano Pernicana.
Another earthquake in a similar magnitude also occured on the northern flank.
The volcano then erupted from the new south-east crater.
The biggest tremor recorded by officials on Monday was magnitude 4.3.
The INGV said in August that the volcano had “grown faster than ever before” over the past few years, even though it often erupts.
In March, a team said the volcano was edging towards the sea at a rate of 14mm per year.