A second volcano has erupted in Papua New Guinea just days after the eruption of Mount Ulawun sent thousands fleeing, sparking fears that scarce humanitarian resources will be stretched even thinner.

Key points: Manam Island is one of PNG's most active volcanoes and is home to roughly 9,000 people

Manam Island is one of PNG's most active volcanoes and is home to roughly 9,000 people An estimated 15,000 people have been evacuated in West New Britain province

An estimated 15,000 people have been evacuated in West New Britain province The provincial government has allocated 2.5 million kina, just over $1,000,000

About 15,000 people are expected to be affected by the first eruption, which began on Wednesday.

Prime Minister James Marape said defence forces would be deployed to assist in the relief work.

A second volcano on the island of Manam in the Madang Province began to erupt with a 'thundering noise' at around 1:00am Friday (local time), Manam islander Bill Sauba told the ABC.

By 5:00am thick smoke and ash was filling the sky.

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"The situation is still continuing … the ash is still falling," Mr Sauba said.

"There is ashfall covering about 6 villages because of the wind direction."

Manam Island, just 10 kilometres wide, is one of the Pacific nation's most active volcanoes and is home to roughly 9,000 people.

Eruptions happen frequently, but Mr Sauba said emergency response teams usually take a long time to respond.

"The usual process is one week — you know after we are all dead — then maybe they come and take reports."

Humanitarian resources already strained after Ulawun

Pilot Eroli Tamara took images of rising smoke as she flew past Thursday afternoon. ( Facebook: Eroli Tamara )

On Wednesday, the sudden eruption of Mount Ulawun, which sent ash as high as 18 kilometres into the air, forced an estimated 15,000 people to flee in the country's West New Britain Province.

Steve Saunders, principal geodetic surveyor for the Rabaul Volcano Observatory, said although the eruption calmed down Thursday, they will continue to monitor it closely.

"Usually volcanos do start very violently … we may get some resumption of activity because the conduit has been opened but hopefully that will be less violent," he told ABC.

"At the moment it's very quiet, and hopefully it will stay that way."

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Local provincial disaster officials have declared a state of emergency and are making plans for evacuated people to remain in care centres for between three and five months.

The provincial government has allocated 2.5 million kina, just over $1 million.

The provincial government in West New Britain is also seeking financial assistance from the national government, local media reported, but PNG Finance Minister, Charles Abel said that could prove difficult.

"One of the issues we face in our budgeting process is to capture an amount that is sufficient to deal with natural disasters," Mr Abel told Parliament on Thursday.

Ulawun is the highest and steepest of all the volcanoes in PNG, according to the Papua New Guinea Geological Survey.

While Ulawun has produced small eruptions periodically for the past few decades, the last eruptions of this scale occurred in September 2000 and again in May 2001.

Manam erupted three times last year — in August, September and December — and twice in January.