A surprise jolt underneath the Philippine's Mayon Volcano, world-renowned for its perfect cone shape until its last eruption in 2010, has claimed 5 lives when the volcano spewed ash early on the morning of Tuesday.

At 8:00 AM, Mayon Volcano produced a small phreatic eruption event that lasted about 73 seconds. The United States Geological Survey (USGS) defined phreatic eruptions as "steam-driven explosions that occur when water beneath the ground or on the surface is heated by magma, lava, hot rocks, or new volcanic deposits (for example, tephra and pyroclastic-flow deposits). The intense heat of such material (as high as 1,170° C for basaltic lava) may cause water to boil and flash to steam, thereby generating an explosion of steam, water, ash, blocks, and bombs."

The Mayon Volcano spewed ash that reached 500 meters above the summit and drifted west southwest. Prior to that, no volcanic earthquake was detected within the past 24-hour observation period. No intensified volcanic activity was likewise seen.

As of 10:30am local Philippine time, the fatality tally has reached five, with seven injured. Four of the fatalities were foreigners. The Philippines' National Disaster Risk Reduction and Management Council (NDRRMC) said among those dead were Indonesian nationals.

The fatalities, whose identities still remained unknown, were all mountain climbers. They died after being hit by huge rocks, according to Kenneth Jesalva, a volcano tour guide who was interviewed earlier by local media outlet ABS-CBN.

Renato Solidum, Philippine Institute of Volcanology and Seismology (Phivolcs) executive director, explained Tuesday's occurrence was a normal thing.

"It is a normal process in any volcano. If you look at Mayon Volcano, it continuously moves steam, even other volcanoes in the country. But once that steam is trapped, there can be pressure and that can trigger a shallow explosion," Mr Solidum said in an interview with local media outlet ANC.

"The steam column that was produced was grayish, but mainly it is water. There is not much pressure on it. There is no new magma yet... The steam carried with it the old ash at the crater of the volcano," he added.

He also pointed out there is no new need to evacuate the residents living near the slope of Mayon volcano because there is no indication the volcano will erupt soon.

However, small phreatic explosions including small steam and ash ejections may occur suddenly with little or no warning.

"It is strongly advised that the public refrain from entering the 6-kilometer radius Permanent Danger Zone (PDZ) due to the threat of sudden steam-driven eruptions and rock falls from the upper and middle slopes of the volcano," Phivolcs said in a statement.