A Philippine volcano has spewed plumes of ash but volcanologists say the steam-driven explosions do not indicate an imminent violent eruption.

Philippine Institute of Volcanology and Seismology director Renato Solidum said Mount Bulusan southeast of Manila ejected ash up to a kilometer (0.6 mile) high for about 10 minutes on Tuesday. A smaller explosion followed hours later and lasted a minute.

He said there were no indications that the volcanic activity involves magma rising from below.

A permanent danger zone is being maintained within a radius of 4 kilometers (2.5 miles).

Bulusan is one of 23 active volcanoes in the Philippines but has not had a violent eruption since 1918.