Over 20,000 tremors have been detected by the Icelandic Met Office (IMO) since late October, with 1,400 in the 24 hours to midday on Thursday.

The heightened geological activity led to the famed Blue Lagoon being closed as a precaution.

It is concentrated in the southwestern Reykjanes Peninsula, which was dormant for 800 years before a 2021 eruption.

The IMO said that magma - molten rock - was accumulating at a depth of around 5km (3m) northwest of Thorbjorn mountain.

The Blue Lagoon is easily visible from the mountain. The owners of the famed turquoise hot springs said they would close the site until 16 November out of concern for employees' welfare.