LEGASPI, Philippines (AFP) -- Troops fanned out Tuesday across the slopes of the rumbling Mayon volcano in the central Philippines to try to enforce a mass evacuation of villagers before a feared deadly eruption.

Volcanologists have warned the scenic mountain could blow at any time and authorities have ordered all 35,000 nearby residents to leave their homes immediately.

The volcano is the country's most active and has erupted around 50 times in the past 400 years, often with deadly consequences. It has been rumbling since February and started spewing lava last month.

So far around 25,000 people have been moved in military trucks to government-run shelters, said the provincial disaster control center in Legaspi City.

The government ordered the mandatory evacuation on Monday after repeated explosions shot giant clouds of smoke and ash into the skies above the mountain, which last erupted in 1993 and killed about 70 people.

President Gloria Arroyo urged residents to comply with the evacuation order, telling them "not to flirt with danger" by going back to their homes inside the eight kilometer (five mile) danger zone declared around the volcano.

"We assure those affected that we have enough resources to shoulder basic needs and services in the evacuation centers; and that the people will not be kept from their homes a minute longer than is necessary," Arroyo said in a statement.

The volcano was quiet on Tuesday morning and its cone-shaped summit obscured by clouds.

But the country's chief volcanologist Ernesto Corpus warned the eruption was now entering a far more dangerous phase that could involve sudden and violent explosions of rock, ash and fumes.

"It is absolutely clear to us that Mayon will blow. What we're seeing now is the shift in its activity from a quiet eruption to a more explosive activity," Corpus said.

However, he said that if the communities followed the government's evacuation orders, the physical and economic fallout would be limited.

Provincial governor Fernando Gonzalez said he hoped the evacuation would be completed Tuesday.

Provincial disaster coordinating council chief Cedric Daep said as many as 70,000 people might need to be moved if the eruption is accompanied by heavy rains that might mix with the volcanic ash to form deadly, fast-moving volcanic mudflows.

A brigade-sized military unit of several thousand soldiers and a fleet of 80 military trucks are enforcing the evacuation.

However several farmers on the slopes of the volcano told AFP they would not leave their homes until the situation became more serious.

Bienvenido Belga said he and about 10 neighbors were remaining on Mayon's slopes staying in a hut while they harvested their crop of copra -- dried coconut meat. He said they did not feel in danger yet. "We need the money. The copra will rot if left there," he said.

"We still have six sacks to bring down."

Ed Laguerta, head of the Mayon volcano monitoring team, said volcanic quakes beneath the crater had been increasing, followed by minor ash explosions that indicate "more pressure inside the volcano."

"In our experience, when these signs can be seen, it might take several days, within a week, before a hazardous eruption can occur."

Laguerta said the lava column that began streaming out of the crater more than three weeks ago was now just two kilometers (1.24 miles) from inhabited areas.

But he said it was contained within two channels and was no threat to people, although it was setting coconut plantations ablaze.

He said the greatest danger would be from pyroclastic flows, the superheated ash and other volcanic material that spurts from the crater and flows down the mountain's flanks at great speed.

He said these flows killed 77 people, mainly farmers, in Mayon's last deadly eruption in 1993.

Mayon has erupted 47 times since records began being kept in 1616. The deadliest eruption came on February 1, 1814, when it spewed masses of lava that buried the town of Cagsawa and killed an estimated 1,200 people.