Europe's most active volcano, Mount Etna in Sicily, erupted on Monday, with officials reporting more than 130 earthquakes of up to 4.3 in magnitude.
The Mount Etna observatory said lava had spewed from a new fracture near its south-eastern crater.
A local volcanologist said it was Etna's "first flank eruption" in more than a decade.
Volcanic ash covered nearby villages, while planes into Catania airport had to be halted temporarily.
A large explosion was felt close to Etna during the morning.
A video filmed 2,500m (8,200 ft) up the 3,350m volcano showed the fast spread of ash. People on the mountainside were told to escape quickly.
Da quota 2500 , video inviato delle guide sentite nel finale le voci che fanno scendere tutti 😵😵Posted by Antonino Longo on Monday, December 24, 2018
Catania airport said later that the airspace had been reopened to allow four planes to land per hour, before confirming it would return to normal operation by 20:00 local time (19:00 GMT).
🔴🇬🇧Update #Etna Volcano: at 8 p.m. december 24th, #Catania airport will be fully functional, without any restrictions. Arrivals and departures can be subjected to delays but the traffic will be normalized. Thanks for your patience and comprehension🎄#CTAairport pic.twitter.com/3rc6LwJPLr— Aeroporto di Catania (@CTAairport) December 24, 2018
Italy's INGV volcanology institute said that during a three-hour period from 08:50 (07:50 GMT) on Monday more than 130 earthquakes took place.
The biggest tremor of magnitude 4 was on the north-east side of Etna near Piano Pernicana, while another of similar magnitude was felt on the northern flank.
That was followed by intense eruptions from the volcano's new south-east crater.
Later on Monday, a magnitude-4.3 tremor was also recorded by officials - the strongest felt throughout the day.
Although Etna has seen frequent eruptions, the INGV said in August that the volcano had grown faster than ever before in recent years.
In March a UK-led team said that the whole structure of Europe's premier volcano was edging towards the sea at a rate of 14mm per year.