At least nine people, including five children, have been killed by a flash flood at a national forest in the US state of Arizona.

More than 100 people were thought to have been at the Cold Springs Swimming Hole in Tonto National Forest when the flood struck on Saturday afternoon.

The group was from Phoenix and Flagstaff and the victims ranged in age from a 60-year-old woman to a two-year-old girl.

Water Wheel Fire and Medical District Fire Chief Ron Sattelmaier said the flood was sparked by a severe thunderstorm in a remote area that had been burned by a recent wildfire.

It is estimated that the water reached a height of 6ft.

Some of the bodies were recovered two miles down-river.

A 13-year-old boy from the same group is still missing.

Four people were rescued by helicopter and taken to hospital with hypothermia.

Mr Sattelmaier said: "They had no warning - they heard a roar and it was on top of them.

"It's pretty much recovery (now). We don't believe there's anybody left out there."

Footage recorded by Disa Alexander shortly after the flood showed a man in a tree holding his baby as water rushed around him.

The man's partner was nearby, also clinging to a tree.

The flooding happened during storm season. The weather was hot and dry where the swimmers were, but heavy rain fell about eight miles upstream.

A flash flood warning was issued but without a radio, the group would not have known.

Mr Sattelmaier said: "I wish there was a way (of) keeping people from getting in there during monsoon season.

"It happens every year."

In 2015, seven people died in Utah's Zion National Park after they became trapped while hiking in a narrow, but deep canyon.

In 1997, a wall of water thundered through Lower Antelope Canyon near Page in Arizona, leaving 11 hikers dead.