Indonesia's Mount Kelud volcano appears to have erupted, a top official has said, based on seismographic signals.

An estimated 350,000 people live within 10km of the volcano on the island of Java, about 90km south-west of the city of Surabaya.

There were no immediate reports of casualties and the area is shrouded in fog, blocking the view of the volcano.

A volcanologist said escalating tremors indicated the first eruption was at 1615 local time (0915 GMT).

The volcano last erupted in 1990, killing dozens of people.

The authorities have been monitoring the peak in East Java for several weeks and raised its alert status to the highest level about two weeks ago as its activity increased.

Armed police last month evacuated more than 100,000 people from the slopes of Mount Kelud - but many later returned to their villages, while others refused to leave.