JAKARTA (XINHUA) - The Indonesian transport ministry has issued a warning to airliners alerting them about volcanic ash from the country's most active volcano Merapi in Java island, spokesman for the ministry Bambang Ervan said.

The warning was issued at 3.56am Jakarta time on Thursday (May 24) by the AirNav Indonesia, the spokesman said.

"The airliners are advised to be cautious about the volcanic ash," he told Xinhua by phone. A further evaluation would be undertaken after the issuance of the advice, said Bambang.

Mount Merapi erupted on Thursday, sending an ash column as high as 6,000m into the sky, Head of National Volcanology Agency Kasbani said.

The eruption, which occurred at 2.55am Jakarta time, was followed by the issuance of poisonous gases, such as H2S and CO2, from the crater, Kasbani said.

"The volcanic gases are dangerous in the areas around the crater, Therefor we restrict activities in the radius of 3km. These gases were on hot condition and created pressure that led them to exit," he told Xinhua by phone.

The official suggested residents in nearby regions set up preparation measures, including using masks.

"Volcanic ashes can be spread far away from the crater by wind blows," Kasbani said.

The eruption forced about 660 people to flee homes, according to the national disaster management agency.

Mount Merapi, situated on the borders of Central Java and Yogyakarta province, is about 28km north of Yogyakarta city, which has a population of 2.4 million. Thousands of people live on the flanks of the volcano.

Mount Merapi volcano, one of Indonesia's 129 active volcanoes, has been regularly erupting since 1948. In November 1994, pyroclastic flow from a large explosion killed 27 people. Another large eruption occurred in 2006.