Experts had initially predicted that the eruption of the fissure near Mount Fagradalsfjall, just 40 kilometres (25 miles) from the capital Reykjavik, would be brief, likely dying out after a few days.

But due to the constancy of the lava flow and based on the first analyses of the magma, they now suspect the eruption could be a long-hauler.

"The eruption rate has been similar since the beginning of the eruption" on March 19, Freysteinn Sigmundsson, a geophysicist at the Institute of Earth Sciences, told AFP.

"We have started to wonder if it may eventually be a long duration eruption."

The relatively controlled lava flow has since the weekend drawn hordes of curious onlookers to the Geldingadalur valley, eager to catch a rare, first-hand glimpse of the hypnotic display of bubbling orange-red molten rock.

Grilled sausages and marshmallows

The authorities block access only sporadically in case of bad weather or high levels of toxic gas emissions.

According to preliminary calculations, the magma emerging from the volcano is almost 1,190 degrees Celsius (2,170 degrees Farenheit).