The hot clouds were visible from Ngipiksari hamlet, Sleman district, Yogyakarta province, at around 10.45 a.m. and moved in the easterly direction to Woro River in Klaten district, Central Java province, local residents said.
The residents of the hamlet who returned home from refugee camps three days ago said Tuesday`s hot clouds were one of the biggest since the Nov 5 massive eruption.
"The hot clouds could be watched for a few minutes before haze blanketed the volcano`s peak," one of the residents said.
Mt Merapi, the world`s most active volcano, had erupted repeatedly in the past two or three weeks but its most fatal eruptions occurred on Oct 26 and Nov 5.
At least 259 people had perished and many others sustained burns and became displaced in the eruptions.
The total number of refugees being sheltered in 639 refugee centers in Yogyakarta and Central Java reportedly reached 367,548.
The volcano`s eruptions spewed hot clouds of ash and lava into the air and sent lava down its many slopes.