This is the highest aviation warning when a volcanic eruption is underway with a significant amount of ash in the atmosphere.
Mount Agung, a volcano on the Indonesian Island of Bali, erupted for a second time in less than a week on Saturday evening, leading several airlines to change flight plans.
General view of Mount Agung during an eruption seen from Kubu sub-district in Karangasem Regency, on Indonesia's resort island of Bali on November 26.
The centre has not felt it necessary to raise the overall alert level, which remains at 3 on a scale of 1 to 4, nor to more strictly limit human activity around the volcano.
Ivanka Trump & Chelsea Clinton Defend Malia Obama, Telling Critics She's "Off Limits"
Chelsea Clinton, the daughter of Bill and Hillary Clinton, tweeted her support too. This is not the first time Clinton has come to the aide of a president's child.
Authorities warned anyone still in the exclusion zone around the volcano, which extends 7.5 kilometres (4.5 miles) from the crater in places, to leave.
Worldwide airlines including Jetstar and Qantas cancelled flights to and from Bali in the wake of the eruption.
Saturday's eruption came just four days after a similar eruption occurred on Tuesday.
Airlines have issued a shock "red warning" about the impending danger of volcanic ash in the skies over Bali, following the second emission from Mount Agung this week.
White House: Trump, Putin set to speak Tuesday
The protests developed into an armed uprising and a civil war that has killed hundreds of thousands of people and displaced millions.
Satellite imagery Sunday showed the volcanic ash drifting east and southeastward towards Lombok Island. Suantika said Agung could spew ash for at least a month but did not expect a major eruption.
Indonesia sits on the "Pacific Ring of Fire" and has more than 120 active volcanoes.
Despite the raised alert status, I Gusti Ngurah Rai International Airport in the provincial capital of Denpasar was still operating as normal, an airport official said.
Magma - molten rock - has now been detected close to the volcano's surface, said officials and volcanologists. About 25,000 people have been prevented from returning to their homes around the volcano since September when activity began for the first time since a 1963 eruption killed about 1,100 people.
AT&T, Comcast win as Trump FCC urges end of Obama web rules
In 2015, the FCC approved a set of regulations on those companies, known as internet service providers. Gutting net neutrality will have a devastating effect on free speech online.