JAKARTA, Indonesia — Rescuers dug through mountains of mud yesterday in search of survivors from landslides in western Indonesia, some using their bare hands because blocked roads delayed the arrival of heavy-lifting equipment.

At least 78 people were feared dead — most of them killed in a single landslide in the Karanganyar district that buried a late-night dinner party, a rescue official said. The victims had just cleaned up a mud-covered home. “They were having dinner together when they were hit by another landslide,” search and rescue chief Eko Prayitno said. “At least 61 people were buried.”

In nearby Wonogiri district, 17 people were feared dead when landslides hit their homes following a half-day of nonstop rain.

Hundreds of soldiers, police and volunteers struggled to get heavy-lifting equipment to villages on the main island of Java, but roads blocked by the mud and flooding were hampering the rescue efforts, Mr. Prayitno said.

Thousands of houses were inundated yesterday, from Java to Sumatra to Sulawesi island, further east, witnesses and news reports said. Some of the fleeing residents tried salvaging their possessions from the rising waters by using tires to float their televisions and refrigerators to higher ground.

A tsunami warning drill on Java was unaffected by yesterday’s landslides.

Seasonal rains and high tides in recent days have caused widespread flooding across much of Indonesia, the world’s fourth most-populous nation. Millions of people live in mountainous regions and near fertile flood plains that are close to rivers.