Heavy rain triggered deadly slides on Sunday and Monday in a remote part of the country.
The UN humanitarian office OCHA said in an update the death toll could rise to as many as 500, citing local officials.
"More than 15,000 affected people need to be evacuated," it added.
Prime Minister Abiy Ahmed is expected to visit the area on Friday.
He said earlier in the week he was "deeply saddened by this terrible loss".
Photos from the scene show residents standing over the shrouded bodies of victims pulled from the muddy earth.
Rescuers have been using hand shovels to pick through the mud.
Many people were buried in the Gofa Zone of Kencho Shacha Gozdi district on Monday, as rescue workers searched the steep terrain for survivors from mudslides the previous day.
Landslides are common during Ethiopia's rainy season, which started in July and is expected to last until mid-September.
Deadly mudslides often occur in the wider east African region, from Uganda's mountainous east to central Kenya's highlands.
In April, at least 45 people were killed in Kenya's Rift Valley region when flash floods and a landslide swept through houses and cut off a major road.
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