A volcano in the central Philippines erupted for a second time this year, prompting emergency evacuations after it spewed a huge of column of ash into the sky, authorities said on Monday.

Mt. Kanlaon, an active volcano straddling the Southeast Asian country's central provinces of Negros Occidental and Negros Oriental, sent an ash cloud up to 4,000 metres (2.5 miles) into the sky at about 3 p.m. (0700 GMT) local time.

The Philippine Institute of Volcanology and Seismology (Phivolcs) raised its alert level to 3 on a scale of 5. Level 3 means there is an increased risk of lava flows and the potential for a hazardous eruption within weeks.

"We are still unable to confirm if this is magmatic eruption. But for now we just call it as explosive eruption," Phivolcs Director Teresito Bacolcol said by phone.

"It may lead to magmatic unrest," he added.

Mt. Kanlaon is one of two dozen active volcanoes in the Philippines, which is located on the Pacific "Ring of Fire" where volcanic activity and earthquakes are common.

"Some local government units (LGU) have started evacuations. There's already ash fall in LGUs near Kanlaon," Bryll Sanor, a disaster agency staff in Negros Occidental province, said by phone.

The civil defence office said emergency evacuations were underway for people living near the volcano, without saying how many had been evacuated so far. About 54,000 people could be affected by the eruption.

"Authorities are preparing for the worst-case scenario of raising the alert level ... which would necessitate further evacuation and safety measures," the civil defence office said in a statement.

The civil aviation regulator said flights near Mt. Kanlaon were operating as normal, but advised pilots to avoid flying close to the volcano.

Negros Occidental and Negros Oriental are major producers of sugarcane.