AUSTIN, Texas (REUTERS) - Some 367 pit bulls, many scarred and emaciated, have been rescued and a dozen people across the south-eastern United States (US) have been charged with dog fighting in what animal advocacy groups called one of the largest such raids in US history.

"The number of dogs seized and the amount of money involved in this case shows how extensive this underworld of dog fighting is," US Attorney for the Middle District Alabama George Beck said in a statement on Monday. "These dog fighters abuse, starve and kill their dogs for the supposed 'fun' of watching and gambling on a dog fight."

The suspects, who come from Mississippi, Georgia, Alabama and Texas, face multiple charges related to dog fighting and gambling, with each charge carrying up to five years in prison.

Dog fighting is a felony in all 50 states and the District of Columbia.

At one site, some 114 emaciated, wounded dogs were found chained to tires, without food and water, and in makeshift shelters in scorching summer heat, rescue groups said.

"Thousands of others all over the country continue to endure unimaginable suffering and death just like this at the hands of dog fighters," said Mr Tim Rickey of the American Society for the Prevention of Cruelty to Animals (ASPCA), which along with the Humane Society of the United States helped remove the dogs.

"We want to end it once and for all."

The US Attorney said in a statement that the charges are the result of a three-year investigation by nearly two dozen state, local and federal agencies. They seized more than US$500,000 (S$639,000), drugs, guns and other evidence in what they called a high-stakes ring that saw bets up to US$200,000 per fight, according to the statement.

This size of this raid is second only in the US to a 2009 case in which more than 500 dogs were rescued and more than 100 people in eight states were arrested, according to the ASPCA.