A wall of floodwater swept away two vehicles carrying women and children in the western United States, killing at least seven people and leaving six others missing.

Three people survived as the flash flooding washed the vehicles carrying 16 people several hundred yards downstream at about 5pm local time on the border of Utah and Arizona, assistant fire chief Kevin Barlow said.

Search and rescue teams called off the search late on Monday due to treacherous conditions in the sister towns of Hildale, Utah, and Colorado City, Arizona, he said.

The floods came after heavy rain fell in the canyons just north of the towns, sending waves of water barrelling through the streets of a community of 7,700 people. The towns are about 315 miles south of Salt Lake City.

The women and children were in two different vehicles, Mr Barlow said - a full size van and an SUV.

Search and rescue teams are scheduled to resume efforts to find the missing people at daybreak.