Jakarta: Indonesia's Anak Krakatau volcano erupted early on Sunday, prompting the temporary suspension of all flights at Jakarta's Soekarno-Hatta International Airport as volcanic ash spread across parts of western Indonesia.

Indonesia's Geological Agency said the volcano, located in the Sunda Strait between the islands of Java and Sumatra, showed signs of increased activity on Saturday before erupting for about 30 seconds at 3:53am on Sunday.

No casualties were reported and no evacuation order was issued. The nearest settlement is more than 16 kilometres from the volcano. However, authorities warned residents and visitors to stay at least three kilometres away from the active crater.

According to Indonesia's Centre for Volcanology and Geological Hazard Mitigation, volcanic ash spread across parts of Jakarta and Lampung province at the southern tip of Sumatra.

In a travel advisory, Soekarno-Hatta International Airport said flight operations were temporarily suspended from 5:30am to 9:30am because of increased volcanic activity.

Passengers at Indonesia's busiest airport sought refunds and collected checked baggage as departure boards showed a growing number of cancelled flights.

Indonesia's volcanology agency and the Darwin Volcanic Ash Advisory Centre in Australia identified two ash clouds using satellite imagery.

One ash plume rose to an altitude of 20,000 feet (6,100 metres) and drifted north-east, affecting parts of Jakarta, Banten, West Java and surrounding waters.

A second plume reached 50,000 feet (15,200 metres) and moved westwards and north-westwards, spreading across parts of Banten, Lampung and Bengkulu provinces, the southern Sunda Strait and areas of the Indian Ocean west of Sumatra.

Anak Krakatau, or "Child of Krakatau", remains one of Indonesia's most closely monitored volcanoes. A major collapse of the volcano in 2018 triggered a tsunami that killed at least 430 people in Sumatra and Java.

Indonesia suspends flights at Jakarta airport after Anak Krakatau eruption