The volcano, on the diving resort island of Siau off Sulawesi and 2,325 km (1,445 miles) northeast of the capital Jakarta, is one of Indonesia's most active volcanoes.

"We've recorded volcanic tremors that indicates more lava will climb to the crater's surface," Simatupang said by telephone from his office in the city of Bandung.

"At least four more villages on the western slope are at risk of being swallowed by lava."

District chief Idrus Mokodompit said another hundred people have left their homes to join nearly 600 people who have already sought refuge in the nearest town.

"The villagers are not allowed to return to their homes until the government lowers the volcano's alert status," Mokodompit said by telephone.

The alert status on the 1,827 metre (5,994 feet) volcano was raised to maximum at the weekend after hot clouds started moving eastwards, posing a threat to hundreds of people.

Another volcano 175 km (110 miles) south of Mount Karangetang has also been spewing ash and sending debris down its slopes.

But Mount Soputan, which lies on the northern tip of the Sulawesi island, is not yet seen as a threat to nearby villages.