A gang of African teenagers have allegedly stabbed an off-duty police officer who was defending a bus driver.

Dave Thorne claims he stepped in to protect a driver who was being verbally abused by the group at a shopping centre in Melbourne's south-east.

The officer was punched from behind after being confronted by a man carrying a stanley knife and a woman carrying a 'pointy weapon', he told 3AW.

A gang of African teenagers allegedly stabbed Dave Thorne (pictured) in the head at a Melbourne shopping centre

Horrific images of Mr Thorne show him lying on a hospital bed with dried blood on his face and the stitches he received to the deep cut on his head.

The gang were 'of African appearance' but he couldn't remember any other details of what they looked like during the attack at Waverley Gardens Shopping Centre.

'As I got off I said something along the lines of 'ease up guys, he's just doing his job,' Dave said.

The gang were 'of African appearance' but he couldn't remember any other details of what they looked like during the attack at Waverley Gardens Shopping Centre. Pictured are the stitches he received to his head

'The male pulled out a box cutter, like a Stanley knife, a female pulled out some kind of pointy weapon.

'I got king hit from behind with something, I don't know what.'

Thorne was rushed to hospital where he stayed for seven hours while he received stitches to his head.

Victorian Police told Daily Mail Australia they expect to make charges.