The Philippines' most active volcano continues to spew huge fountains of red-hot lava and massive ash plumes, and authorities warn a violent eruption may occur in days or even hours. Lava fountains gushed up 700 metres (2,300 feet) above Mount Mayon's crater on Tuesday (23 January) and ash plumes rose up to three kilometres (1.9 miles) in the sky.

The said the volcano appeared to be entering a new phase characterised by more rumblings and pyroclastic flows — superheated gas and volcanic debris that race down the slopes at high speeds, vaporising everything in their path.

An explosive eruption at noon on Monday was the most powerful since the volcano started acting up more than a week ago. Photos and videos show a towering ash cloud and spectacular lava fountains. The dazzling but increasingly dangerous eruption has sent 40,000 villagers to shelter in evacuation centres.

The eruptions have plunged nearby villages into darkness during daytimes and sent lava, rocks and debris cascading down Mayon's slopes.

Volcanic ash fell in more than a dozen towns in Albay and nearby Camarines Sur province on Monday, with visibility being heavily obscured in a few towns because of the thick grey ash fall, Jukes Nunez, another Albay provincial disaster response officer, told the Associated Press by telephone. "It was like night time at noon, there was zero visibility in some areas because the ash fall was so thick," Nunez said.

There have been no reports of deaths and injuries. Aeroplanes have been ordered to stay away from the crater and ash-laden winds and several domestic flights have been cancelled.

After Monday's huge explosion, officials raised Mayon's alert level to four on a scale of five, and the danger zone was expanded to 8 kilometres (5 miles) from the crater, requiring thousands more residents to be evacuated, including at least 12,000 who left their homes and then returned during gentler eruptions.

Some villagers returned to the area to check on their homes and farms, while others sneaked back to watch a cockfight in an arena in Albay's Santo Domingo town despite the risks and police patrols and checkpoints, said Cedric Daep, a provincial disaster-response official.

In a sign of desperation, Daep told a news conference that he has recommended electricity and water supply be cut in communities within the no-go zones to discourage residents from returning. "If pyroclastic flows hit people, there is no chance for life," Daep said. "Let us not violate the natural law, avoid the prohibited zone, because if you violate, the punishment is death penalty."

With its near-perfect cone, Mayon has long been popular with climbers and tourists but has erupted about 50 times in the last 500 years, sometimes violently. The 8,070-foot (2,460-metre) volcano has generated tourism revenues and jobs in Albay Province.

In 2013, an ash eruption killed five climbers who had ventured near the summit despite warnings. Its most destructive eruption, in 1814, killed more than 1,200 people and buried the town of Cagsawa in volcanic mud. The belfry of Cagsawa's stone church still juts from the ground in an eerie reminder of Mayon's fury.

Mayon volcano
Tourists are pictured posing for photos at the famous Cagsawa ruins, with the backdrop of the Mayon volcano, in 2009 Ted Aljibe/AFP

The Philippines, which has about 22 active volcanoes, lies in the "Ring of Fire," a line of seismic faults surrounding the Pacific Ocean where earthquakes and volcanic activity are common. In 1991, Mount Pinatubo in the northern Philippines exploded in one of the biggest volcanic eruptions of the 20th century, killing about 800 people, covering entire towns and cities in ash and partly prompting the US government to abandon its vast air and naval bases on the main northern Luzon island.