The northern town of Laiza bordering China's Yunnan province has reported flash flooding since early Monday, when muddy waist-high waters began to stream through the streets.

Laiza is a stronghold of the Kachin Independence Army (KIA), which has for decades commanded control of its own ethnic enclave and emerged as one of the most powerful factions in Myanmar's civil war.

"A lot of water flowed down the mountain to the river," said KIA spokesman Naw Bu.

"The flow of water was too strong and destroyed areas surrounding the river," he added. "Six people were killed in the flood and 100 houses were destroyed."

Rescue operation had begun on Wednesday, he said, but were being hampered by road blockages.

"All of the roads have been damaged and the roads disappeared in some areas," said one resident, who declined to be named for security reasons. "The water rose suddenly."

More than 3.5 million people are currently displaced in Myanmar amid the civil war sparked by a 2021 coup, many sheltering in temporary camps, leaving them exposed to the elements.

The resident said flooding was "terrible" around local camps for the displaced where some shelters had been swept away and people had been wounded.

Myanmar is in the midst of its monsoon season when daily deluges are common.

But scientists say hazardous weather events are becoming more frequent and severe around the world as a result of human-driven climate change.