MANILA, Dec. 27 (Xinhua) -- The Philippines' most active volcano, Mount Mayon, spewed grayish white ash plume that rose 500 to 600 meters above the crater Thursday morning, a Philippine volcanologist said.

Eduardo Laguerta, a resident volcanologist at the Philippine Institute of Volcanology and Seismology (Phivolcs), Albay province of northern Philippines, told Xinhua that the phreatic eruptions or steam-driven explosions occurred at 8:17 a.m. and 8:28 a.m. local time, adding that no major eruption is expected.

Phivolcs said the volcano is at a "moderate level of unrest," prompting the authorities to warn residents to stay out of the volcano's 6-km danger zone due to possible "sudden explosions."

The 2,460-meter cone-shaped volcano is located in Albay province, approximately 300 km southeast of Manila on the island of Luzon.

In a bulletin issued on Thursday, Phivolcs warned that "sudden explosions, lava collapses, pyroclastic density currents and ash fall can occur and threaten areas in the upper to middle slopes" of the volcano.

Before the steam-driven explosions, the institute said it has recorded one volcanic earthquake during the past 24 hours.

"Moderate emission of white steam-laden plumes that crept downslope before drifting southwest and west-southwest was observed. Fair crater glow from the summit could be observed at night," the bulletin read.

Mount Mayon last erupted in January this year that prompted the authorities to evacuate thousands of villagers.

The volcano is a popular tourist destination in northern Philippines. It is famed for its near-perfect cone but has a long history of deadly eruptions. It has erupted 51 times during the last 400 years.

The Philippine archipelago straddles the Pacific Ring of Fire and is prone to earthquakes and volcanic eruptions.