Hitoyoshi, Kumamoto Prefecture, on July 4, 2020. (Kyodo)

TOKYO - Photos and videos of submerged houses and cars in torrential rain in southwestern Japan inundated social media on Saturday, with trapped people calling for help and others assuring families and friends of their safety.

"My friend's (house) is submerged due to the Kuma River overflowing...and (my friend) is currently waiting for help on the 2nd floor of the house," along with an elderly person, a post on Twitter showed, with a picture of a submerged car in flood water.

Torrential rain in the southwestern Japan prefecture of Kumamoto triggered massive flooding Saturday, with heavy rain expected to continue through Sunday.

The Kumamoto prefectural government said residents in some cities and villages were stranded after the flooding.

Another Twitter post with a photo of a mountain in the background and houses submerged up to the roof read, "I want to go somewhere safe. I'm worried about tonight and scared of the mountain collapsing. Everyone is scared but let's hang in there together because we want to survive."

Similar posts were shared and circulated on social media calling for help for friends and residents stranded in their homes or awaiting rescue on rooftops. Photos and videos also showed residents standing by fallen trees and muddy water flowing into houses.

"The Kuma River has overflowed...I have failed to escape," another post read, with video of a muddy stream flowing to the writer's feet.

Other contributors on Twitter were offering advice and lessons from the torrential rain disaster in western Japan in 2018.

"Even in areas which are not flooded, water supply could be cut off after the rain stops. Make sure you have as much water as possible in plastic bottles," the post read.

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Hitoyoshi, Kumamoto Prefecture, on July 4, 2020. (Kyodo)