"Anak Krakatau has been erupting, but it is not dangerous. In fact, it is a sight to see," Simatupang said. "If the weather is good, you can see a beautiful mountain with lava coming down from its crater and blasting red flames."

Sciestists monitoring Anak Krakatau said the volcano had blasted burning rocks 95 times since Thursday night.

Indonesia has the highest number of active volcanoes of any country, sitting on a belt of intense seismic activity known as the "Pacific Ring of Fire".

Anak Krakatau, which lies 42 km (26 miles) from the nearest observation post in Serang on the westernmost edge of Java, is one of four Indonesian volcanoes that have rumbled to life in recent weeks.

It gradually formed after the volcanic island of Krakatau blew up in a massive eruption in 1883, triggering tsunamis and killing more than 36,000 people.

Ashes from that eruption, one of the most devastating natural disasters in recorded history, were carried by upper level winds as far away as New York City.

Authorities have advised people to stay out of a 3-km zone around Anak Krakatau, where tourists often land from small boats to scramble up its newly formed slopes.

Scientists said on Thursday they had lowered the alert level on Mount Kelud, in East Java, to the second highest level because of a decline in its activity and advised thousands of people who had fled to government shelters to return to their homes.