MANILA — A major explosion of the Philippines' restive Taal volcano no longer appears imminent, authorities said on Sunday as they partially lifted a mass evacuation order but warned residents should still remain ready to flee.

Warning signs like earthquakes have been steadily waning since Taal burst to life two weeks ago, prompting at least 135,000 people into evacuation centres over fears of a massive eruption.

The nation's seismological agency said steadily shrinking ash and gas emissions were signs of "decreased tendency towards hazardous explosive eruption", leading them to drop the alert by a notch.

The immediate impact of the reduced warning was provincial authorities lifting the evacuation order for nearly all the towns that ring the volcano, a tourist attraction that sits in the middle of a lake.

"Residents of all towns under lockdown except Agoncillo and Laurel now have the option to return," local governor Hermilando Mandanas told a press conference.

"There's a possibility that the volcano may still erupt and we should still be ready to evacuate in one hour."

The volcano shot ash 15km high and spewed lava in the January 12 eruption, which crushed scores of homes and killed livestock as well as crops.

However, seismologists warned the volcano could imminently unleash a much bigger eruption, posing a deadly risk to anyone in a 14km radius "danger zone".

Taal, located just 60km from the capital Manila, is one of the most active volcanoes in a country where eruptions and earthquakes are a dangerous part of life.

Its last eruption was in 1977, but it has a long history of activity. In 1965, a Taal eruption killed some 200 people.

The most powerful volcanic explosion in the Philippines in recent years was the 1991 eruption of Mount Pinatubo, about 100km northwest of Manila, which killed more than 800 people. — AFP