Philippines beefs up troops around restive volcano

The crater of the Mayon volcano glows as lava cascades down its slopes, in Legazpi city, 500 km (310 miles) south of Manila December 19, 2009.

LEGASPI, Philippines (Reuters) - The Philippines sent more troops to impose an expanded no-go zone around the country's most active volcano as it neared a hazardous and possibly explosive eruption, officials said on Monday.

Mayon Volcano, known for its near-perfect cone shape in the coconut-growing central Bicol region, has been spewing ash and burning mud and rocks for about a week, the state vulcanology agency said.

Authorities raised the alert level to 4 on Sunday after Mayon showed increased volcanic activity. Rumbling sounds were growing louder, nearly 2,000 volcanic quakes were recorded and lava fountains shot debris as high as 200 metres (650 feet).

Level 4 indicates an eruption is imminent and the maximum alert level of 5 means an eruption is underway.

Tens of thousands of people have been evacuated from the slopes of the volcano, with the help of the army.

"We doubled our strength. We added more troops," Captain Razaleigh Bansawan, army spokesman in the Bicol region, told reporters. "What we are doing is that we are intensifying our checkpoint operations along the 9-11 km (5-6 mile) danger zone."

Bansawan said the security measures were designed to prevent casualties in case of a major eruption which was expected to occur within days. Troops were imposing a 24-hour curfew in the no-go zone and moving people at the volcano's base to safety.

Nearly 50,000 people had been evacuated to temporary shelter areas in eight cities and towns in Albay province, where Mayon is located.

Food and water stations have been set up. Face masks have also been distributed to lessen the impact of ash particles in the air.

Local authorities appealed for more portable toilets, other sanitation facilities and potable water to prevent outbreak of disease.

The Philippines lies on the "Ring of Fire", a belt of volcanos circling the Pacific Ocean that is also prone to earthquakes.

Mayon is the most active of 22 volcanoes in the country, having erupted more than 50 times in the past four centuries. The most destructive eruption was in February 1841, when lava flows buried a town and killed 1,200 people.

The last time Mayon erupted was in 2006.

(Reporting by Manny Mogato; Editing by Raju Gopalakrishnan and Sugita Katyal)