Helka, one of Iceland’s most feared volcanoes is showing signs it could blow, raising fears of a new ash cloud crisis.

The volcano – known as  the Gateway to Hell – is close to Eyjafjoell, which erupted last year and sent out a cloud of ash which brought European air traffic to a halt.

As a result, more than 100,000 flights and eight million passengers were affected.

The Iceland Civil Protection Authority is now closely monitoring the situation at Hekla.

"The movements around Hekla have been unusual in the last two to three days," University of Iceland geophysicist Pall Einarsson told Iceland Review.

“While this might not necessarily mean an immediate blast, the volcano is ready to erupt."

But geophysicist Ari Trausit Gudmundsson told AFP that an eruption of Hekla is unlikely to impact flights.

He said it usually erupts with both lava and ash and if the next eruption is like previous ones, it is unlikely to cause any disruption.

Last month, the Puyehue volcano in Chile began erupting, with its ash plume twice disrupting flights in Australia and New Zealand over a period of weeks.