LEGAZPI, Philippines, December 23, 2009 (AFP) - Mount Mayon shot a column of ash high into the sky Wednesday as Philippine officials said the volcano was becoming increasingly active.

The kilometre- (half-mile-) high column alarmed residents and officials who had been bracing for a major explosion since last week, when Mayon started oozing lava and belching steam and ash.

It also blanketed surrounding villages and towns with a thin layer of fine particles that health officials warn could cause respiratory and skin problems.

"That (ash plume) is not yet an explosive eruption. That is just a minor ash explosion," government volcanologist Alex Baloloy told AFP from an observatory in Legazpi, about 330 kilometres (200 miles) southeast of Manila.

"Every day, it has been acting like this. The numbers and figures (of quakes and ash) may change but our observations show its monitored parameters remain intense," he said.

He said the alert level remained at four on a five-point scale, meaning that a major eruption could happen within hours or days. Level five means a hazardous eruption is already occurring.

Baloloy said Mayon's volcanic activity, such as rumblings, quakes and emissions of sulphur dioxide, were still increasing, indicating that a hazardous eruption could happen any time.

The government has already evacuated more than 47,000 individuals living inside an eight-kilometre (five-mile) danger zone around Mayon to 26 evacuation centres in anticipation of a hazardous eruption.

The 2,460-metre (8,070-foot) volcano, which is famed for its near-perfect cone, has erupted 48 times in recorded history. In 1814, more than 1,200 people were killed as lava buried the town of Cagsawa.

Its latest eruption was in 2006, when it oozed lava and vented steam and ash for two months. While no one perished from the eruption, a powerful typhoon three months later dislodged tons of debris that had collected on its slopes, burying entire towns and killing over 1,000 people.