Galeras volcano in southern Colombia, near the border with Ecuador, began erupting late Saturday, and some 8,000 residents were ordered to evacuate, the Colombian Institute of Geology and Mines said.
A forceful eruption began at 7:10 pm (0010 GMT), after which the regional alert system was raised to its highest level, local emergency relief coordinator Lina Dorado told AFP.
A "large amount of ash" was falling on the regional capital Pasto, reported the provincial governor.
The Civil Defense and Red Cross agencies has begun evacuation procedures to help the 8,000 people living on the slopes to get off the volcano.
The 4,270-meter (14,009-foot) Galeras has stirred sporadically in recent years. It erupted in January 2008, causing no casualties, but a 1993 eruption claimed the lives of nine people.