Indonesia yesterday ordered flights to steer clear of Anak Krakatau as it raised the danger alert for the erupting volcano to the second-highest level and widened a no-go zone around it, heightening fears of another natural disaster striking the tsunami-hit coastal areas around the Sunda Strait.
The national geological agency raised the danger alert for Anak Krakatau to three on the four-level scale.
"The affected flights (around Anak Krakatau) have been diverted and given alternative routes," Mr Yohanes Harry Douglas, the spokesman for government air traffic control agency AirNav, said in a statement.
Flights to and from Soekarno-Hatta, Indonesia's main international airport just outside the capital Jakarta, continued to operate as normal. There were no disruptions to domestic or international flights.
Jakarta is about 155km east of the volcano.
Last Saturday, an eruption of the volcano in the Sunda Strait, which separates Java and Sumatra, caused a section of the crater to collapse and slide into the ocean, displacing a large volume of water and triggering waves as high as 5m.
At least 430 people have been killed, with 1,495 others injured and another 159 missing after the tsunami slammed into coastal areas in western Java and south Sumatra.
Nearly 22,000 people have been evacuated and are living in shelters.
The volcano has been rumbling on and off since July, but has been particularly active since last weekend.
The authorities have warned that the crater of Anak Krakatau remains fragile, raising fears of another collapse and tsunami, and have urged residents to stay away from the coast. They have also expanded the current 2km-radius no-go zone around Anak Krakatau to 5km.
"Since Dec 23, activity has not stopped... We anticipate a further escalation," said Mr Antonius Ratdomopurbo, secretary of the geological agency.
Anak Krakatau recently spewed columns of ash up to 3km high, even as aid workers and rescuers struggled to reach communities reeling from the devastation wreaked by last Saturday's killer wave.
Ash from the volcano's continued eruptions fell on Cilegon and parts of Serang in Banten on Wednesday afternoon, blown in by the north-easterly winds, said Dr Sutopo Purwo Nugroho, the spokesman for Indonesian's national disaster management agency (BNPB).
Images shared by BNPB showed a thin layer of soot covering houses, buildings and vehicles along the west coast of Java.
The authorities said the ash was not dangerous, but advised local residents to wear masks and goggles when they were outdoors.
The volcanic island, whose name means "Child of Krakatau", emerged around 1927 after its "parent" Krakatau erupted in 1883, killing more than 36,000 people.
The Indonesian archipelago sits on the Pacific "Ring of Fire", which makes it susceptible to earthquakes and volcanic eruptions.
Saturday's volcano-triggered tsunami was Indonesia's third major natural disaster in the past six months, after a series of earthquakes on Lombok in July and August and a quake-tsunami in September that killed about 2,200 people in Palu, Sulawesi.
Last week's tsunami came just days before the 14th anniversary of the Dec 26, 2004 tsunami disaster which killed 226,000 people in 14 countries, including more than 120,000 in Indonesia.
• Additional information from Reuters
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