Koalas, wallabies, crocodiles and birds have been found tortured and mutilated in a spate of cruel attacks on animals in north-eastern Australia.

Wildlife rescue officers discovered a four-year-old male koala with its hind legs cut off on a property at Clear Mountain, near Brisbane earlier this week. A post-mortem found the gumleaf-loving marsupial was clubbed to death, and its hind legs had been butchered off after it died.

It is the second savage attack on a koala this month. Last week a mother koala and her baby joey were found severely beaten in a park about 18miles (30km) away in Kallangur, while another joey was found dumped in a bin. It had its skull crushed and injuries consistent with it being beaten to death.

Police and officials from the RSPCA, the animal welfare charity, are looking for a group of local men, aged 20-25, who are apparently known to police and are suspected to have been involved in the attacks.

They are the latest in a string of senseless attacks against harmless Australian wildlife – both in the wild and in captivity.

Similar attacks have taken place on crows and magpies in the Brisbane area in the past month. A crow was found with its wings sawn off and left to die hopping around a supermarket car park, while magpies and cane toads were found nailed – alive – to trees in a park at Kallangur.

In May vandals shot dead a dozen wallabies and baby paddymelon - a small kangaroo-like marsupial - on a crocodile farm at Innisfail, far north Queensland.

The attackers systematically slaughtered the animals, shooting them through the chest and stomach, and also flooded tanks holding 300 young crocodiles.

RSPCA Queensland spokesman Michael Beatty, said the attacks are “very disturbing”.

“There are obviously some very sick people out there,” he said. “There’s not much difference between animal cruelty and other forms of abuse. Somebody who does this, torturing defenceless animals, there’s obviously something wrong with them, they certainly need to be apprehended and have some sort of psychological counselling.”

The maximum sentence for people found guilty of animal cruelty in Australia is two years jail, or $75,000 (38000.)

There are approximately 100,000 koalas in Australia, according to the Australian Koala Foundation. Along with the kangaroo they are the country's most iconic animal.

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