COPENHAGEN: A volcano spewed lava and smoke over southwestern Iceland for a second day on Friday raising fears of spreading pollution hours after its eruption forced the evacuation of a spa resort.

Fountains of glowing molten rock shot into the night sky when the volcano first erupted on the Reykjanes peninsula on Thursday.

The flow from the volcano has since slowed, Rikke Pedersen, head of the Nordic Volcanological Centre, said. "We have a quite intense fountaining and high output in the beginning and it rapidly declines, but that doesn't tell us anything about how long it will last."

The meteorological office warned that wind could carry gas pollution from the eruption towards the south and southeast.

The nearby Blue Lagoon spa, which has large outdoor pools heated by geothermal energy, was evacuated late on Thursday and said it remained closed on Friday.

"We just went there as tourists looking for a good day," said real estate broker Dennis Murphy, from Cape Cod, Massachussets, who was there with his daughter.

"The next thing you know, the ground is exploding right next to us," the 53-year-old said. They watched the sky turn red as they were being evacuated.

"There was definitely a sense of urgency as we were trying to get out of there. The staff was throwing all of our belongings into our bag and just saying, you got to get out of here," he added.

Around 1,300 guests and staff were at the spa, Icelandic daily Morgunbladid reported.

Lava initially flowed out of the volcano at a rate of up to 2,000 cubic metres (70,600 cubic feet) per second, making it comparable to the last eruption in May, Pedersen said.

The length of the fissure in the volcano, which has erupted six times since December, expanded to 5km (3.1-miles) during the day from 3.9km late on Thursday, Pedersen said.

The nearby fishing town of Grindavik, which was threatened by burning lava and hit by earthquakes during some earlier eruptions, was not directly impacted, the meteorological office said.

Lava flows stopped short of a nearby road, Pedersen said.

Air traffic in and out of the capital's Keflavik Airport was not affected, it said on its website on Friday.