Sinabung volcano in Sumatra and Java's Merapi erupt, hitting flights

Two volcanoes erupted in Indonesia yesterday, one forcing flights to be rerouted and delaying the return home of thousands of people who had previously been evacuated.

Mount Sinabung on western Sumatra island, which has been erupting on and off since mid-September, shot volcanic ash 8,000 metres into the air, the Geological Disaster Mitigation and Volcanology Centre said.

"The transport ministry is redirecting flights away from a certain path because of Mount Sinabung's latest eruption," ministry spokesman Bambang Ervan said.

He said the affected routes were commonly used by international flights to and from Australia, as well as domestic flights.

The eruption also meant about 5,000 people who had recently been evacuated from the area around Sinabung due to its eruptions could not return home.

"This is the biggest eruption in vertical terms since September," vulcanologist Agus Budianto said.

On the main island of Java, Indonesia's most active volcano, Mount Merapi, spewed a column of ash and smoke 2,000 metres into the air in the morning.