Indonesia evacuating thousands after volcano erupts, as tsunami ...

Indonesian rescuers have raced to evacuate thousands of people after a volcano erupted five times, forcing authorities to close a nearby airport and issue a warning that the crater collapsing into the sea could cause a tsunami.

Mount Ruang's crater flamed with lava against a backdrop of lightning bolts overnight after eruptions pushed an ash column more than a mile into the sky and forced authorities to raise their alert to the highest level of a four-tiered system.

Taka, a local fisherman who only gave one name, was at sea helping people to safety by boat when the crater unleashed a fiery orange column.

"There was a mix of fire and rocks. Lava flowed in various directions," he told AFP.

Authorities said they were rushing to evacuate more than 11,000 residents from the area around the volcano.(AFP: Center for Volcanology and Geological Hazard Mitigation)

The volcano sits on a remote island in Indonesia's outermost region and has a peak 725 metres above sea level. It was still billowing a column of smoke up to 800 metres high on Thursday morning, officials said.

Houses on Tagulandang, another remote island nearby, were riddled with holes from falling volcanic rocks on Thursday, rescuers said, and residents were preparing to leave at least temporarily.

"The road condition … is covered by volcanic material," rescuer Ikram Al Ulah told AFP by phone from the Tagulandang seaport.

"Many people are still wandering around. Maybe to evacuate precious goods from their house."

There were no reports of deaths or injuries but authorities said they were rushing to evacuate more than 11,000 residents from the area around Tagulandang, which is home to about 20,000 people.

Tourists and residents were warned to remain outside a 6 kilometre exclusion zone.

Some residents were already trying to flee in a panic, according to officials.

"People evacuated on their own … due to the volcano's eruption and small rocks that fell," local search and rescue agency official Jandry Paendong said in a statement on Thursday.

"The people scattered to find evacuation routes."

He said 20 staff were helping evacuate residents along the coastline near the volcano on rubber boats.

Authorities also evacuated a prison on Tagulandang, ferrying 17 inmates along with 11 officials and 19 residents by boat to Likupang seaport in northern Sulawesi island, according to rescuer Ikram Al Ulah.

More than 800 people were initially taken from Ruang to Tagulandang after the first eruptions overnight Tuesday, before further eruptions on Wednesday prompted evacuations from that wider zone.

Indonesian military personnel load food items onto a ship as they head to the island near Mount Ruang volcano.(AFP: Adolof Buol)

Those displaced gathered at temporary shelters on Tagulandang and were given mats, blankets and masks by authorities.

The navy sent a warship to deliver aid and help the evacuation effort, it said on Thursday, while North Sulawesi police sent dozens of officers.

The warship evacuated 195 people from Tagulandang to Bitung, a coastal city in North Sulawesi, on Thursday evening, a navy spokesperson told AFP.

Authorities also warned of a possible tsunami as a result of the eruptions.

"The communities in Tagulandang island [need] to be on alert for … [a] tsunami caused by the collapse of the volcano's body into the sea," volcanology agency head Hendra Gunawan said in a statement on Wednesday.

Tourists and residents were warned to remain outside a 6 kilometre exclusion zone.

The authorities' fears were compounded by previous experience.

The crater of Mount Anak Krakatoa between Java and Sumatra islands partly collapsed in 2018 when a major eruption sent huge chunks of the volcano sliding into the ocean, triggering a tsunami that killed more than 400 people and injured thousands.

Indonesia, a vast archipelago nation, experiences frequent seismic and volcanic activity due to its position on the Pacific "Ring of Fire".

Mount Ruang's eruption led to the closure of Sam Ratulangi International Airport in Manado city, located more than 100 kilometres from the volcano, until midnight Thursday.

The airport hosts airlines that fly to Singapore, South Korea and China.

Budget airline AirAsia said it also cancelled flights to and from nine airports in eastern Malaysia and Brunei until Friday morning.

The volcano's last major eruption was in 2002, also requiring the evacuation of residents.

AFP