Two volcanoes erupted in Indonesia on Monday, with one forcing flights to be rerouted and stopping thousands of people who had already been evacuated from returning home.
Mount Sinabung on western Sumatra island, which has been erupting on and off since mid-September, shot volcanic ash around 8,000 metres (26,000 feet) 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 in a statement.
It also meant that more than 5,000 people who had recently been evacuated from the area around Sinabung due to its eruptions were unable to return home.
On the main island of Java, Indonesia's most active volcano, Mount Merapi, spewed a column of ash and smoke some 2,000 metres (6,500 feet) in the morning, said Sutopo Purwo Nugroho, chief of the National Disaster Mitigation Agency.
He said the eruption, which was triggered by small earthquakes, prompted around 600 families to rush to evacuation posts but they were returning home as there was no imminent threat.
Mount Merapi killed more than 350 people in a series of violent eruptions in late 2010 when it also destroyed entire villages.
Indonesia has dozens of active volcanoes and straddles major tectonic fault lines known as the "Ring of Fire" between the Pacific and Indian oceans.
In August five people were killed and hundreds evacuated when a volcano on a tiny island in East Nusa Tenggara province erupted.
Explore further: More than 15,000 flee volcano in Indonesia