Some 3,000 residents were being evacuated from Magelang district Wednesday, bringing the number of residents evacuated this week to around 11,000, most of whom were being evacuated for the second time after fleeing weeks ago before the volcano first erupted.

''Evacuation is still underway,'' Edi Susanto, a district official, told Deutsche Presse-Agentur dpa. ''We will evacuate a total of 11,000 from 14 danger zones.''

While authorities were stepping up evacuation efforts in some areas, residents from other areas were returning to their homes on the slopes of the volcano, despite the lingering threat of an eruption.

''Everyone left these temporary shelters after staying no more than 36 hours,'' Misman, an official at makeshift shelter in Umbulharjo, told DPA. ''I don't know the reason why they returned home. They just left here without notice.''

Misman, who like many Indonesians goes only by one name, said the residents were among more than 2,000 people from three hamlets near Mount Merapi that were evacuated on Sunday evening, after the most active volcano spewed hot clouds of gas and lava down its crater.

''We reminded them that they have to stay alert and to be ready at certain points for evacuation should Merapi go out of control,'' Misman said. ''In line with the advice from the volcanologists, we warned those residents living near Gendol river to stay away. At least 300 metres from its bank has to remain vacant.''

Unlike other volcanoes which have vertical eruptions, firing lava and debris high into the sky, the eruption at Merapi, however, flows down its sides, affecting only the surrounding areas, experts said.