Mount Soputan began rumbling close to midnight on Saturday, with increasing frequency of tremors, and finally belched heatclouds and ash at around 5:00 am (2200 GMT Saturday), said Yudi Juhara from the nearby vulcanology office in Tomohon.

The heatclouds, with temperatures reaching as high as 600 degrees Celsius (1,112 Fahrenheit), did not fall far from the crater, Juhara said, adding that there were no human settlements on the slope of the vulcano threatened.

"The wind blew the ash to the east and northeast and even we here in Tomohon have been covered by a thin film of ash from the Soputan," Juhari said.

Tomohon is some 10 kilometers (six miles) northeast of Soputan.

He said people living on the slopes of the 1,830 meter (6,112 foot) high volcano had been warned to remain alert for any signs of eruptions but had not been asked to leave their villages.

Juhari said tremors continued to be felt at the vulcanology's office observation outpost in Maliku, some four kilometers from the crater.

Earlier on Sunday, the smoke column rose some 500 meters high but clouds have since covered the top of the mountain.

So far there has been no report of any casualty or damage, he said.

Soputan spewed heatclouds and ash in a similar outburst in October. It last erupted in 2002 but caused no casualties.

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