Authorities have already suspended operations at a local airport in the town of Maumere, some 60km west of Lewotobi, the airport said on Instagram.
The geology agency said residents near rivers should also remain on alert for hazardous floods of volcanic material known as lahar if heavy rain occurs.
In July, the same volcano spewed a colossal 18km tower of ash, forcing the cancellation of 24 flights at the international airport on the resort island of Bali.
Indonesia, a vast archipelago nation, is situated on the Pacific “Ring of Fire”, an arc of intense and frequent seismic activity stretching from Japan through Southeast Asia and across the Pacific basin.
– Agence France-Presse