A volcano in the Philippines has begun spewing lava, as authorities warn that a "hazardous eruption" is possible "within hours or days".

In the early hours of Monday weak lava began flowing out of Taal volcano- located some 70km (45 miles) south of the capital Manila.

It comes after it emitted a huge plume of ash triggering the evacuation of some 8,000 people from the area.

Taal is the Philippines' second most active volcano.

It is one of the world's smallest volcanoes and has recorded at least 34 eruptions in the past 450 years.

"Taal volcano entered a period of intense unrest... that progressed into magmatic eruption at 02:49 to 04:28... this is characterised by weak lava fountaining accompanied by thunder and flashes of lightning," the Philippine Institute of Volcanology and Seismology (PHIVOLCS) said in a statement.

But PHIVOLCS director Renato Solidum said that signs of a hazardous eruption, including "flows of ashes, rocks, gas at speeds of more than 60 kph horizontally" had not yet occurred, according to CNN Philippines.

PHIVOLCS has now raised the alert level from 3 to 4, out of a maximum of 5.

The volcano is located on an island in the middle of the Taal lake and the authorities also warned of a possible "volcanic tsunami".

A volcanic tsunami can be trigged by falling debris after an eruption, pushing the water and generating waves.

On Sunday, the volcano emitted a giant plume of ash, with rumbling sounds and tremors also reported.

Ash fell on several areas nearby with residents advised to wear masks. One resident in metro Manila said shops had begun to run out of masks.

"When I went to my car, I saw it was covered in ash. I hurriedly went to buy a mask from a drugstore but they had run out," Angel Bautista, a resident of Paranaque told Reuters.

The volcano ash has forced the city's international airport to suspend all flights. PHIVOLCS warned that the "airborne ash and ballistic fragments from the eruption... posed hazards to aircrafts".

The Philippine stock exchange also announced it would halt all trading.

President Rodrigo Duterte's office has also ordered the suspension of government work in Manila and of all schools across all levels in the capital.

Earthquakes and volcanic activity are not uncommon in the Philippines, which lies along the Ring of Fire - a zone of major seismic activity which has one of the world's most active fault lines.