Indonesia's most active volcano, Mount Merapi, has erupted, sending a column of volcanic materials as high as 5,500 meters (18,045 feet) into the sky.

Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho said the eruption Friday morning happened suddenly and was accompanied by a rumbling sound with medium to strong pressure.

There were no immediate reports of casualties, and local authorities have asked people living within 5 kilometers (3.11 miles) of the crater to evacuate.

The 2,968-meter (9,737-foot) mountain on the main Java Island 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.