LEGAZPI CITY, Philippines -- The Philippine Institute of Volcanology and Seismology (Phivolcs) raised the alert status around Mayon Volcano from Level 1 to Level 2 Friday morning after it observed intensified restiveness in the volcano.

This alert condition signifies a state of increasing unrest, which could lead to ash explosions or eventually an eruption, a Phivolcs bulletin said.

Since June, monitored parameters indicated an increase in the current activity of Mayon Volcano, Phivolcs said.

"The number of recorded low-frequency volcanic earthquakes rose to higher level, signifying possible movement of magma beneath the volcano's edifice at shallow depth," it said.

A study on Thursday showed that the current seismic count on Mayon was at the same level when a phreatic (steam-driven) explosion occurred in August 2008.

Eduardo Laguerta, Phivolcs resident volcanologist, said a ground uplift or swelling of about one centimeter was measured by a precise leveling survey conducted from June 15 to June 22 and the uplift was sustained during a resurvey on Thursday.

Both residents around the volcano and Phivolcs scientists noted that the glow at the summit crater has intensified and could now be observed at the Lingon Hill Observatory here even without a telescope.

However, the steaming level, which reveals the amount of sulfur dioxide emission from the crater, was at a moderate level.

An aerial survey conducted last Wednesday morning showed a cone-shaped pile of hot, steaming old rocks, possible remnants from previous eruptions, which could be the source of the glow at the crater, Laguerta said.

The bulletin said that the low-frequency volcanic earthquakes and ground uplift could indicate that fresh volcanic materials were moving upward, causing the formation of the cone-shaped pile of materials at the crater.

Phivolcs strongly recommended that people stay away from a six-kilometer-wide area around the base of the volcano, known as the permanent danger zone, and an extended seven-kilometer wide area on Mayon’s southeastern flank because of the threat of sudden explosions and rockfall.

Active river channels and those areas perennially identified as lahar-prone in the southeast sector should also be avoided, especially during bad weather or when there is heavy and prolonged rainfall, Laguerta said.

Albay Governor Joey Salceda said in a text message to the Philippine Daily Inquirer (parent company of INQUIRER.net) that the province was ready and making additional preparing because of the alarming condition of Mayon.

"There is also a need to call for an emergency meeting with the city and municipal disaster coordinating council chairs concerned," Salceda said.

Salceda said he instructed provincial personnel to coordinate with telephone companies to expedite the earlier requested land line for the Phivolcs observatory center at Lingon Hill to enable it to release regular bulletins to media outfits in the province.

The provincial government has discouraged mounting climbing and the picking of orchids on the volcano's slopes, said Cedric Daep, director of the Albay Provincial Safety and Emergency Management Office.

"The farmers are also advised to avoid sleeping in their huts after tending their farms along Mayon's slopes in the daytime to avoid getting caught offguard by pyroclastic flows," Daep said, adding that the his office was also in the process of assessing the population at risk to prepare them in case an evacuation is ordered.