Mount Merapi, which has been smouldering for three weeks, is threatening to erupt on the Indonesian island of Java.
The volcano has been spewing gases, ash and lava, prompting officials to raise the threat status to the highest level.
The evacuation of thousands of people living on the slopes has been ordered.
Thousands of people, mainly the elderly and mothers with young children, had already been voluntarily moved to temporary shelters.
But many villagers are reluctant to leave their homes and livestock.
The Red Cross is providing emergency food and health kits for those who fled their homes.
Mount Merapi - about 30km (18 miles) from the town of Yogyakarta - had its last major eruption in 1994, when 36 people were killed.
The 2,914m (9,560-foot) volcano is one of Indonesia's most active, producing major eruptions roughly once a decade.