Mount Gamalama erupted to spew lava and ash on Ternate in eastern Indonesia, prompting thousands of residents to flee the volcano on one of the former Spice Islands.
There were no immediate reports of casualties after the 1,715-metre-high (5,650-foot) volcano first erupted late on Sunday.
Residents grabbed warm clothing before fleeing their houses, with many taking refuge at the local governor's house.
We advised residents to use masks and the local authority to close the airport until everything is normalized, said Surono, head of Indonesia's Centre of Vulcanology and Geological Disaster Mitigation.
He said many residents were returning to their homes, although authorities were keeping the volcano at the second highest level of alert, he said.
The Sultan Babullah airport in the provincial capital of Ternate shut Monday, said Pujobroto, corporate secretary at PT Garuda Indonesia, which flies twice a day to the city in the Molucca chain of islands.
The volcano has clove groves on its foothills, one of the spices that led the Portuguese and Dutch to settle there several centuries ago, and Ternate city is the business centre for an island group now becoming known for nickel mining.
Indonesia, the world's fourth most populous country, is on the Pacific Ring of Fire and is frequently prone to natural disasters such as earthquakes, volcanoes, tsunamis and floods.
(Reporting by Jakarta Bureau; Editing by Neil Chatterjee and Ron Popeski)