Activity at an Icelandic volcano subsided some Thursday, but an expert warned it still looked ready to blow, as magma pressure underneath Mount Hekla was stronger than before its last eruption.

"Activities at Mount Hekla have calmed down a little bit," said University of Iceland geophysicist Pall Einarsson, who sounded the alarm on Wednesday that Hekla looked ready to erupt.

Gunnar Gudmundsson, a geophysicist at the Icelandic Meteorological Office, also told AFP "things have calmed down some (and) there have been no earthquakes".

While such observations are promising, volcanoes are notoriously temperamental and Einarsson cautioned an eruption still appeared imminent.

"Measurement of the magma pressure indicates that it has been more in the last few days than before the volcano's last eruption in 2000," he told AFP, adding: "it is a fact that Hekla is ready to erupt and that could happen at any time".

The Hekla volcano is close to the ash-spewing Eyjafjoell, which last year caused the world's biggest airspace shutdown since World War II, affecting more than 100,000 flights and eight million passengers.

The volcano, dubbed by Icelanders in the Middle Ages as the "Gateway to Hell", is one of Iceland's most active, having erupted about 20 times over the past millennium, and about once a decade for the past 50 years.

Hekla eruptions are known to be extremely varied and hard-to-predict, with some lasting only a matter of days and others lasting months and even years.

While scientists say a blast at Hekla would probably not produce as much ash as Eyjafjoell or the Grimsvoetn eruption in May and thereby not as many flight disruptions, there is concern for people in the surrounding area.

"If people are in the wrong place at the wrong time they can be in danger. The last time Hekla erupted in 2000 the state radio gave an half an hour warning and that is not neccesarily enough for people who are in area," warned Anders Hansen, the head of the Hekla Museum in nearby Leirubakki.

At 1,491 metres (4,892 feet) and located about 110 kilometres (70 miles) east of Reykjavik, Hekla is so active that scientists estimate about 10 percent of the tephra -- the solid matter ejected when a volcano erupts -- produced in Iceland over the past millennium, or about five cubic kilometres, comes from this one volcano.