Iceland is bracing itself for a volcanic eruption that will arrive within “hours or days”, experts have warned.

Around 3,000 residents have evacuated the southwestern town of Grindavik close to the Fagradalsfjall volcanic system in the Reykjanes region.

Over the past 48 hours, Iceland has faced a seismic swarm as 1,485 earthquakes have hit the country. In addition, a magma tunnel is forming underground beneath the town, which South Iceland’s Volcano and Natural Hazards group believe could be 12km long.

The UK foreign office has updated its travel advice, warning that a volcanic eruption is increasingly likely, but it has not warned against travel with flights still touching down at Keflavik International Airport.

The Icelandic Meteorological Office said on Saturday there was a “considerable” risk of an eruption on the Reykjanes peninsula because of the size of the underground magma intrusion and the rate at which it was moving.

Iceland is highly susceptible to natural disasters as it lies on the Mid-Atlantic Ridge – a divergent plate boundary where the North American Plate and the Eurasian Plate are moving away from each other, leading to volcanic eruptions and earthquakes.

“I don’t think it’s long before an eruption, hours or a few days. The chance of an eruption has increased significantly,” Thorvaldur Thordarson, professor of volcanology at the University of Iceland, told state broadcaster RUV.

Páll Einarsson, professor emeritus in geophysics, told RUV: “Considering the intensity, it must be considered probable that there will be an eruption from this magma tunnel, but it is impossible to say where and how long that fissure will be.”

Despite the imminent threat of a volcanic eruption, the UK Foreign Office has not warned against travel to the region.

Its official warning reads: “Earthquakes and indications of volcanic activity have increased above normal levels on the Reykjanes peninsula, southwest of Reykjavik.

“The Icelandic authorities continue to monitor the area closely, particularly the area northwest of Mt Thorbjörn near the Svartsengi power plant and the Blue Lagoon. On 10 November, a Civil Protection Alert was declared after an intense swarm of earthquakes.”