CHilean Volcano Puyehue
© Constanza YañezThe Puyehue volcano eruption, as seen from the Chilean side.
The entire city of San Carlos de Bariloche turned dark as ash spewed by the nearby Chilean volcano Puyehue began falling all over town. Meanwhile, the Civil Defence Municipal Board called an emergency meeting to decide on how to proceed.

Authorities told the population to remain calm, to keep their water reserves and to remain home at all times in order to avoid the falling ash. In case of an emergency, officials have suggested the use of face masks in order to avoid it.

As an orange alert was declared, authorities shut down the airport.

Earlier, five quakes ranging between 4.6 and 4.8 in the Richter scale had been registered in the south of the Neuquén province, while a few kilometres away, across the border with Chile, some 600 people were evacuated due to the sudden eruption.

The quakes' epicentre was near the town of Villa La Angostura, and they all took place between yesterday and today, local Río Negro newspaper assured.

Even though Security and Civil Defence Secretary David Tressens assured that there is no apparent relation between the quakes and the volcano eruption, on the other side of the border, Chilean authorities have already evacuated over 600 people from the area surrounding the volcano, where eleven quakes have been registered since yesterday.

The volcano, which had remained dormant for decades, began belching ash over 10 km into the sky and prompting the Chiean government to evacuate several thousand residents, authorities said.

The eruption in the Puyehue-Cordon Caulle volcanic chain, about 575 miles (920 km) south of the capital, Santiago, also prompted Chilean authorities to shut a heavily traveled border crossing into Argentina.

It was not immediately clear which of the chain's four volcanoes had erupted because of ash cover and weather conditions. The chain last saw a major eruption in 1960. Local media said the smell of sulfur hung in the air and there was constant seismic activity.

"The Cordon Caulle (volcanic range) has entered an eruptive process, with an explosion resulting in a 10-kilometre-high gas column," state emergency office ONEMI said.

It was the latest in a series of volcanic eruptions in Chile in recent years. Chile's Chaiten volcano erupted spectacularly in 2008 for the first time in thousands of years, spewing molten rock and a vast cloud of ash that reached the stratosphere. The ash also swelled a nearby river and ravaged a nearby town of the same name.

The ash cloud from Chaiten coated towns in Argentina and was visible from space.

Chile's Llaima volcano, one of South America's most active, erupted in 2008 and 2009.

Chile's chain of about 2,000 volcanoes is the world's second largest after Indonesia. Some 50 to 60 are on record as having erupted, and 500 are potentially active.