Impressive footage has emerged of Indonesia’s Anak Krakatau volcano sending clouds of ash and grey smoke into the air on Sunday (December 23).

An eruption on Saturday (December 22) resulted in the collapse of the volcano's southwestern flank which triggered a tsunami that killed at least 400 people and displaced thousands.

Indonesian authorities have raised the alert level of the volcano and expanded the exclusion zone to a five-kilometre radius. Airlines have been ordered to avoid the airspace above the volcano.

This is the moment and condition of the Anak Krakatau mountain after the Tsunami hit the Sunda Strait in Indonesia.

On video filmed on Sunday, December 23, a puff of volcanic smoke from the eruption of the Anak Krakatau volcano appeared.

Western Region Volcano Mitigation Officer, Krisyanto, said on the media that the type of eruption of Mount Anak Krakatau had changed after the tsunami on December 22, 2018.

Changes occurred after the volcanic wall collapsed due to the eruption which triggered the Sunda Strait tsunami. From septimel satellite imagery, officers compared the condition of the mountain during December 11 to December 23, where differences were found, namely the presence of parts or sectors that were landslide in the southwest. The landslide suspected cause tsunami.

Meanwhile, the Center for Volcanology and Geological Disaster Mitigation (PVMBG) on Thursday 27 December raised Anak Krakatau mountain status to be alert or level-3. The community was asked not to approach the crater within a 5 kilometer radius.

The tsunami caused by the eruption of Anak Krakatau has caused deaths toll.