Twenty-five pitbulls rescued from an online dog-fighting racket run by South Koreans in the Philippines have been put down, and another 215 could be also destroyed, rescuers said Tuesday.

All the dogs, rescued by police from a farm south of Manila Friday, could end up being destroyed unless people come forward to adopt the least aggressive ones that can still be nursed back to health, vet Wilford Almoro said.

Most are weakened by dehydration and poor nutrition, and many of those that were destroyed had serious injuries, said Almoro, of the Philippine Animal Welfare Society, a charity that rescues and rehabilitates abused animals,

The remaining dogs "condition could go downhill in the coming days, and if no one will help, then they would have to be put down as well," he told AFP.

Seventeen dogs with the worst injuries were put down on Saturday, including one that had half its tongue ripped out and another with both its ears bitten off, said Almoro.

Eight other dogs were destroyed Tuesday, and another five were set to be put down later in the day, he added.

"Some have unhealed wounds, but most are down to skin and bones and their rib cages are showing," Almoro said, adding most had scars from being wounded in fights.

"They appear to be suffering from dehydration and they are just lying down on the ground where they are tethered."

He estimated that physical rehabilitation for all the animals would cost 3.34 million pesos (about $78,000) and they would also need treatment to correct their aggressive behaviour.

"Just imagine the amount of work required for their continuous upkeep... I don't know if people can raise money for that 24/7," he added.

After police raided the two-hectare (4.94-acre) farm, they arrested 12 people, including eight South Koreans accused of running the illegal dog fights that were streamed live on the Internet to spectators who placed bets.

Dog fighting does not have a large following in the Philippines, unlike cockfighting, which is the country's most popular sport and sees roosters with metal spurs tied to their legs forced to fight to the death.

Almoro said the dogs had been kept in abominable conditions, tied up with chains, in an orchard hidden from view by high walls of sheet metal.

"They were constantly exposed to pain, trauma, and deep wounds. Given their condition, many of them would likely get infected if they remained here," he said.

"Putting them up for adoption is easier said than done, because you have to make sure you are not handing them over to people who would sell them back to dog-fighting gangs."

He urged the Philippine parliament to amend and toughen up the law against animal cruelty, now punishable by a maximum prison term of two years and a 6,000-peso fine.