Authorities have issued a "top alert" status and banned residents and tourists from approaching the Sileri crater at the Dieng volcano complex, said Supriyanto, a spokesman for Banjarnegara district.

He said the last eruption was 19 years ago. "Such a thing normally occurs once in 20 years."

The Sileri crater has belched out hot lava containing sulphur since last week, he said, and half a hectare (1.2 acres) of potato plantations had been destroyed.

Villagers have not been ordered to evacuate their homes because the volcano is located one kilometer from residential areas, the official said.

The Indonesian archipelago has some 127 active volcanos along what is known as the Pacific Ring of Fire.

TERRA.WIRE