TOKYO (AP) — Japan has raised alert levels on a small southern volcanic island, urging its 150 residents to prepare for an evacuation amid growing risks of an eruption.

Japan Meteorological Agency on Wednesday raised the warning for Kuchinoerabu island from two to four on a scale of five. The agency says it has detected an increased activity at the island's Shindake volcano. It had the last major eruption in May 2015.

Local authorities told residents within the 3-kilometer (2-mile) range to start preparing to leave in case of a violent eruption.

The agency cautioned against a possibility of getting hit by volcanic rocks and pyroclastic flows during an eruption.

Kuchinoerabu, a small island with a population of about 150, is south of Japan's southern main island of Kyushu.