Indonesia's most volatile volcano spewed smoke and ash Monday, forcing hundreds of people to flee their villages along its slopes, a disaster official said.
Mount Merapi on the main island of Java rumbled as heavy rain fell around its cloud-covered crater, said Sutopo Purwo Nugroho, disaster mitigation agency spokesman.
The volcano unleashed a column of dark red volcanic material 1,000 meters into the air, and the ash made the rain thick and muddy in several villages as terrified residents fled to safety, he said.
The sound was heard 30 kilometers away, but an eruption did not occur and the volcano's alert level was not raised, Nugroho said.
The 2,968-meter mountain is the most active of 500 Indonesian volcanoes. Its last major eruption in 2010 killed 347 people.
Indonesia, an archipelago of 240 million people, is prone to earthquakes and volcanic activity because it sits along the Pacific "Ring of Fire," a horseshoe-shaped series of fault lines.