Prime Minister Shinzo Abe on Monday pledged full support for victims of last week's massive landslides in Hiroshima, as he made his first visit since the disaster to the western Japanese city.

The death toll from the mudslides, which buried dozens of homes, rose to 54, with a further 28 people missing as of Monday, according to Hiroshima police.

Those missing include a newly-wed couple in their 20s, who had moved to the area just a month before the tragedy.

The young wife was seven months pregnant, local media said.

Some 3,000 rescuers, including soldiers, were continuing to dig through mud and debris at the various disaster sites on the outskirts of the city, but their round-the-clock search was occasionally hampered as fresh rain stoked fears of further landslides.

"The government wants to closely coordinate with the local authority," said Abe, who wore the light blue protective clothing Japanese politicians often don during disasters to signify they are part of the recovery effort.

"We will do our best to have victims return to normal life as soon as possible," he told reporters.

More than 1,600 people were taking refuge in schools, town halls and other public buildings on Monday.

The city has issued evacuation advisories and orders for more than 150,000 residents with heavy rain expected in Hiroshima later in the day.

"It is possible that (search) operations will be suspended again if rain intensifies," a Hiroshima City official said.

"We are watching the situation closely, looking for any alarming signs such as water coming down from mountains becoming murky," which could indicate another landslide is imminent, he said.

Abe had initially planned the visit on Sunday but bad weather forced a postponement.

Huge downpours have hit large parts of Japan over recent weeks, sparking several localised floods and landslips.