Mount Lewotobi Laki-Laki on Flores island erupted late Tuesday and again at 01:35 am (1735 GMT), sending volcanic materials 10 kilometres (6.2 miles) above its 1,584-metre-high peak, the national volcanology agency said in a statement.

There was no immediate word of any casualties or damage, but authorities warned residents and tourists on the eastern Indonesian island to keep away from the area, preparing for possible evacuations.

Geology agency head Muhammad Wafid said it had raised the volcano's alert level to the highest late Tuesday, after detecting an increase in deep quakes that often precede an explosive eruption.

Wafid said the towering column of ash from the eruption could "disrupt airport operations and flight paths if it spreads" further.

Authorities have already suspended operations at a local airport in the town of Maumere, some 60 kilometres (37 miles) 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 18-kilometre (11-mile) 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.