Indonesian volcano erupting slowly: volcanologist

"The lava has been coming out through the cracks in the old lava from the 1990 eruption and created a new lava dome which is now 70 metres (230 feet) high," volcanologist Saut Simatupang told AFP.

The dome first appeared on Saturday night, when volcanologists mistakenly thought a large eruption was occurring so they abandoned their posts.

Simatupang said that the volcano had been making an "effusive" eruption, meaning the energy release has been gradual and not strong enough to dramatically tear through the frozen magma left behind after the last eruption, which killed 34.

"As the energy is not quite strong enough, the lava has only snuck through the cracks and continuously grown inside the crater's lake," he added.