JAKARTA, May 22 (Xinhua) -- Mount Merapi, the most active volcano in Indonesia, spewed a column of ash 3,500 meters to the air early Tuesday, triggering evacuation, a disaster agency official said.

The volcanology agency has risen alert level of the volcano located in main Java Island from the lowest to the second highest, spokesman of national disaster management agency Sutopo Purwo Nugroho said.

"All climbing activities, except for research purpose, is barred in the radius of 3 km from the crater," he told Xinhua in a text message.

The volcano witnessed four times eruptions since Monday with the latest one at 01:47 a.m. on Tuesday, sparking rains of ash in Sleman and Klaten districts, the spokesman said.

"Since last night the people have evacuated. The number of evacuee keeps rising," said Sutopo.

About 660 people have taken shelters to safer grounds, and the national disaster management agency would persistently coordinate with provincial disaster agency in anticipating the hike of the alert level, he said.

Mount Merapi is situated about 28 km north of Yogyakarta city which has a population of 2.4 million and thousands of people live on the flanks of the volcano.

Mount Merapi volcano has regularly erupted since 1948. In November 1994, pyroclastic flow from a large explosion killed 27 people, and another large eruption occurred in 2006.