Washington, Jun 12 (DPA): Heavy rains overnight triggered flash floods in the US state of Arkansas, killing at least 20 people at a popular camping area, state officials said Friday.

"There are some children among the deceased," said Tommy Jackson of the Arkansas Department of Emergency Management, but he couldn't provide an exact number.

Scores of others are believed to be injured, trapped or remain missing near the Albert Pike camp ground near the rain-swollen Little Missouri river in western Arkansas, local TV station KARK reported.

Arkansas Governor Mike Beebe was on his way to survey the damage Friday afternoon and announced the death toll had risen to 20 from an earlier figure of 16 dead, local media reported.

The Arkansas governor's office said the river swelled from about 1 metre Thursday evening to over 7 metres by early Friday morning. The flood waters came in forcefully and swiftly, sweeping away campers and lifting cabins off their foundation.

Police were still determining whether the victims were residents or campers. The area is rural, rugged and remote, with none or patchy cellphone service. It was difficult to estimate how many people were at risk because there had been no registration of residents in the area, Beebe told CNN.

"According to preliminary and unconfirmed reports from the Red Cross, there are about 300 people in the camp ground area," Beebe said.

A massive search-and-rescue mission was launched on foot, by car, on horseback and by helicopter, said police spokesman Bill Sadler. "It's going to be a while before we have reliable communications from that area," he said.