Thousands of people living near the Philippines's most active volcano have begun leaving their homes as lava trickled down its slopes and authorities warned of a dangerous eruption.

Mayon, a volcano famed in equal parts for its near-perfect cone and brutal volatility, had begun to stir again with magma rising to the top and small earthquakes rattling deep inside, authorities said.

"A hazardous eruption is possible within weeks," the director of the state volcanology agency, Renato Solidum, told AFP.

Residents within an five-mile (8km) radius will be forcibly evacuated, said the regional civil defence director, Bernardo Alejandro.

He said authorities expect to evacuate almost all of the 50,000 people in the danger zone – a coconut farming area near the Pacific coast – within three days.

"We'll have no problems with the 99% who will evacuate but there are some who will be hard-headed," Alejandro said, citing the response to a similar evacuation call in 2009 when some farmers refused to move out.

"They don't want to leave their houses and their livelihood … these are coconut and orchid farmers with chickens, pigs and carabaos [water buffalo]."

The local tourist industry was expecting Mayon's latest burst to be a mini-boom. The area, about 200 miles (330km) south-east of Manila, is already a draw for visitors who want to see Mayon's cone, sample the region's cuisine and visit its beaches.

"This will boost local tourism … it's like a party, people are out at night watching," said Marti Calleja, who runs all-terrain vehicle tours near the volcano for as many as 100 tourists a week.

"It's dramatic, like a fireworks show … when there's nothing happening (in the volcano) it's all dark around here, but now it's picture-perfect," Calleja told AFP.

Calleja said that when Mayon became active in the past, his clients often requested night tours to see the glowing crater.

Aljon Banares, who works for a backpackers' inn 7.5 miles (12km) from the volcano, was also preparing for more visitors. "We have more guests in situations like this. Tourists want to see the lava flows," Banares said.

Four foreign tourists and their local tour guide were killed when Mayon last erupted, in May 2013. However, they were on the volcano's slopes at the time, and Banares said tourists would not be in danger if they acted sensibly.

"We tell our clients that it's safe as long as they follow the government's warnings," he said.

The 2,460-metre (8,070ft) Mayon has a long history of deadly eruptions.

In 1814, more than 1,200 people were killed when lava flows buried the town of Cagsawa.

An explosion in August 2006 did not cause deaths directly, but four months later a passing typhoon unleashed an avalanche of volcanic mud from Mayon's slopes that killed 1,000 people.