Indonesia's disaster agency says the death toll from the weekend tsunami has climbed to 373.

Disaster agency spokesman Sutopo Purwo Nugroho said Monday that 128 others were missing in the disaster, with 1,459 injured. The waves washed ashore along  western Java and southern Sumatra islands Saturday night following a volcanic eruption.

Hundreds of military personnel and volunteers combed debris-strewn beaches Monday looking for victims.

It is the latest in a string of natural disasters to strike Indonesia in 2018, making it the deadliest year in more than a decade.

"People said 'run, run a wave is coming!'. There were three waves in a row," said Yadi, a middle-aged fisherman who operates a fleet of six vessels that were among dozens  that sank or were dragged out to sea by the waves. "There was a real panic. Many people were left behind," he said, adding that he and his family escaped by running to higher ground.

What's left behind is a wasteland of collapsed houses and hotels and muddy roads strewn with twisted metal and wood.

Thousands of displaced and grieving residents were searching for missing loved ones on Monday and trying to salvage whatever they could of their belongings.

Heavy equipment was being used to help with the rescue effort. Medics were sent in with the military, while groups of police and soldiers searched remote areas.

Cici Paramita, 27, was clambering through the shattered remains of her house, a tangle of water-logged debris, 50 metres from the beach. "We lost all our belongings," she said.

On Saturday night, she said she had to wade through waist-deep water to rescue her eight-year-old son who was trapped in debris.