Indonesia has warned two volcanoes are at the risk of tremors and eruptions, according to the national Antara news agency on Friday.
The authorities have raised the status of the Mount Anak Krakatau, in Banten province, to level III because of its frequent eruptions, and also put the Mount Slamet, in Central Java, on alert status because it has been showing an increasing activity.
The Mount Anak Karakatau is now dangerous for visitors, said Jumono, an official of the mountain monitoring team in Serang district of Banten province.
He said, according to the monitoring instruments, the Mount Anak Karakatau made 175 eruptions, 23 volcanic quakes and 87 tremors on Wednesday.
Therefore, the Mitigation and Geological Disaster Center (PVMBG)in Bandung told visitors and fishermen to keep at a safe distance of 1 km from the mount.
"If we get close to the area of the mount, it is feared we will be affected by the outpouring of lava from the mount," Jumono said.
On the other hand, Sukedi, an official monitoring Mount Slamet's activity, said Friday that the volcano had spewed hot lava since Thursday, the Jakarta Post website reported.
He recorded a total of 52 small explosions from the volcano but said that the volcano had not yet reached its peak activity.
"Bigger explosions are expected," Sukedi added.
As the volcano's activity increased, local people were drawn out from their homes to the fireworks-like display of lava sparks leaping from the volcano rim. They even cheered every time the volcano spewed hot lava.
Indonesia, with a population of over 230 million, sits on a vulnerable quake-hit zone called "the Pacific Ring of Fire," where two continental plates meet, causing frequent seismic and volcanic movements.