Activity has declined since Friday evening when a growing lava dome partially collapsed, causing Merapi to lose around 1.3 million of 4.3 million cubic metres of lava and volcanic material and become more stable.

Merapi belched 20 clouds and 150 lava flows on Sunday, and 25 and 145 respectively the previous day, said Triyani of the vulcanology office in Yogyakarta, the main city just south of the volcano.

On Sunday, the searing clouds reached four kilometers (two miles) down the south-southeast slope while the longest lava trails stretched three kilometers, she said.

In the first six hours of Monday, the volcano released six clouds, but only one was noticeable from observation posts on its slopes and it only reached one kilometer down, Yani said. Merapi also emmitted 81 lava trails, but only stretching 2.5 kilometers, she added.

"We still need time to observe the trend before deciding whether to lift or maintain the 'beware' status," she told AFP, referring to the top alert status given to Merapi on May 13, meaning an eruption was thought to be imminent.

Merapi's activity settled slightly after it was put on the alert but escalated following a strong earthquake on May 27 that killed more than 5,800 people in and around Yogyakarta.

More than 18,000 residents evacuated from the volcano's flanks are spending the nights in makeshift camps in safer zones.

Merapi's deadliest eruption occurred in 1930 when more than 1,300 people were killed.

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