Police are investigating a horrifying 'Pet Alcatraz' where unwanted dogs are left to die in the Philippines.

Authorities discovered dozens of hapless canines abandoned on Shell Island - a desolate patch of land a boat ride away from mainland Cebu province.

Local animal welfare advocate Janice Palermo sounded the alarm after a friend informed her of the vile animal dumping grounds.

She travelled to the islet, which is visible from the nearby Cebu-Cordova Link Expressway, and rescued 12 emaciated dogs on August 14.

Heartbreaking footage shows Janice and her team luring the starving mutts with trails of kibble. The wary animals gathered to eat before being caught in nets and taken back to Cebu City.

Janice said: 'Someone informed me that dogs known to bite or are no longer wanted by their owners are sent to Shell Island. I couldn't rescue all of them. It was difficult because some were so evasive and scared of people.'

Local boatmen allegedly admitted they were paid between 100 and 200 PHP (1.3 and 2.6 GBP) to ferry the abandoned animals to the island.

Speaking on condition of anonymity, one of them said: 'The owners complain that it's too expensive to send the dogs to the city pound. So the dogs are given to me instead to dump on the island. They pay me to do it.'

The Cebu City Veterinary Office said the cruel pet owners were being tracked down.

Dr Alice Utlang, head of the city vet office, said: 'They have liabilities based on animal welfare, because that is already abandonment. Abandonment is already a form of cruelty.'

Cebu City officials said they were coordinating with the Cordova municipality government which has jurisdiction over the island.

Last year, dozens of stick-thin cats and dogs were saved from an island in Pagadian, southern Philippines, abandoned by owners on another 'Animal Alcatraz'.

The Animal Kingdom Foundation (AKF) said they rescued more than 24 pets and placed them under veterinary care.

Authorities and animal welfare groups then held seminars to educate residents on responsible pet ownership.

Under Republic Act 8485 or the Animal Welfare Law, those found guilty of abandonment may be face one to three years in prison, and fines ranging from 30,000 to 250,000 PHP (405 to 3,400 GBP).