By Agence France-Presse
Anak Krakatau -- a small volcanic island that emerged from the ocean a half century after Krakatoa's deadly 1883 eruption -- has rumbled back to life in recent weeks, spitting flaming rocks and ash from its crater.
No one lives on Krakatau, which forms a small island in the Sunda Strait between Java and Sumatra, but the peak is a popular tourist spot.
Indonesia's geological agency has not raised the alert level for the mountain. However, there is a one kilometre no-go zone around its summit.
When Krakatoa erupted in the 19th century, a jet of ash, stones and smoke shot more than 20 kilometres (12 miles) into the sky, plunging the region into darkness, and sparking a huge tsunami that was felt around the world.
The disaster killed more than 36,000 people.
Indonesia is situated on the Pacific "Ring of Fire", a vast zone of geological instability where the collision of tectonic plates causes frequent quakes and major volcanic activity.