* Mudslides feared as lava, hot gases melt snow

* Officials say little damage so far

* Bursts of lava visible in the sky overnight (Updates with evacuation order, troops sent)

By Simon Gardner

SANTIAGO, April 4 (Reuters) - Chile's Llaima volcano, one of the most active in South America, spewed out a river of lava more than 1,100 yards (1,000 metres) long on Saturday in a fresh eruption, prompting officials to order dozens of people to evacuate.

Llaima, which lies in Chile's picturesque lake region about 435 miles (700 km) south of the capital Santiago, erupted on Jan. 1, 2008, and has belched rock and ash sporadically since then.

The lava and hot gases from the latest eruption are melting snow on the sides of the volcano, and authorities say some towns are in danger of being hit by mudslides.

"We are going to start the evacuation of some people who live in sectors that are particularly vulnerable to the risk of ... avalanches of mud due to melting snow," Johaziel Jamett, head of the early warning center at the National Emergency Office, told Reuters.

"It is a spread-out population. We are talking about a few dozen people, not a massive evacuation," he said.

Twelve people have been evacuated from the Conguillio national park surrounding Llaima, including two tourists. Police have closed the park, and troops have been dispatched to the area, the emergency office said.

MINIMAL DAMAGE

It said an ash-swollen river near the volcano had swept away a pedestrian bridge, but there was no other damage. Bright red bursts of lava were visible in the night sky as Llaima erupted.

The office said on its website that there were "permanent explosions that reach 600 metres (650 yards) above the crater. Falling ash is visible and ... a flow of lava of more than 1,000 metres (1,100 yards) has been observed."

Chile's chain of some 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.

The 10,253-foot (3,127-metre) Llaima was the second to erupt in the past year.

The Chaiten volcano, 760 miles (1,200 km) south of Santiago in the Patagonia region, erupted last May for the first time in thousands of years, spewing ash, gas and molten rock and prompting the evacuation of thousands of people.

Ash from Chaiten soared 20 miles (32 km) into the sky, swelled rivers and caused floods that damaged dozens of houses and destroyed much of the nearby town of the same name.

Chaiten erupted again in February, leading to the evacuation of residents who had rejected a government plan to abandon the town and rebuild it a few miles (km) away. (Editing by Xavier Briand)

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