An off-duty policeman has needed multiple stitches to his head after being attacked by a group of youths who were verbally abusing a bus driver.

Dave Thorne was riding on the bus in Mulgrave, in Melbourne’s southeast, when he noticed about 10 youths hurling insults at the driver.

“I said something along the lines of ‘ease up guys, he’s just doing his job’,” Mr Thorne said today.

“I wasn’t interested in starting a fight.”

The senior constable was taken to hospital following the attack, and required a dozen stitches on his head. (3AW) (9NEWS)

A group of about 10 youths targeted Mr Thorne after he departed the bus. (9NEWS/3AW) (9NEWS)

The senior constable departed the bus, but was followed by the youths who quickly became violent.

One offender allegedly pulled out a box cutter, while another revealed a pointy-edged weapon.

“I got king hit from behind with something,” he said.

Mr Thorne was left bleeding in the gutter, with a nearby security officer thankfully noticing him and calling for help.

Photos published by 3AW’s Neil Mitchell showed the bloodied victim in a neck brace soon after the attack.

Mr Thorne was taken to Dandenong Hospital and required 12 stiches to his head and also suffered bruising to his legs.

Mr Thorne spoke about the violent incident today. (9NEWS) (9news)

Despite the ordeal, he encouraged the public to speak out for what is right no matter the risk.

“It’s better to stand up than lie in bed going, ‘gee I wish I’d done something about that’.

“I’ll wear (the injuries) any day of the week.”

A 16-year-old Glen Waverly man has been interviewed by police following last Thursday’s incident.

He is expected to be charged on summons.

Investigations are ongoing.