Police are searching for more members of a group accused of a vicious attack on two St Kilda police officers in Melbourne's inner south, which left one requiring surgery.

Key points: Two police officers were responding to reports of an assault when they were attacked

Two police officers were responding to reports of an assault when they were attacked Three men and a woman have been charged over the assault and are due to face court

Three men and a woman have been charged over the assault and are due to face court Superintendent Tony Silva described the alleged attackers as "cowardly" and "behaving like animals"

Grainy mobile phone vision released by police shows two officers surrounded by a group of people, and one officer being repeatedly slammed against the road.

Four people have been charged over the assault, which took place about 3:00am on Sunday, and police believe at least three other people were also involved.

Superintendent Tony Silva said police were in the process of arresting a man over an alleged assault on a "vulnerable person" when they were set upon.

Two police officers were taken to hospital after the attack, which Superintendent Silva described as cowardly.

One officer suffered a torn bicep muscle, which required surgery.

The other suffered injuries including bruising and swelling around the eye, including possible damage to his eye socket.

"It shows [the officer] on the ground, with his face to the ground with this rather heavyset person above him grabbing him by the shoulders and ragdolling him, smashing his head against the ground," Superintendent Silva said.

"I would describe it as ragdolling him, smashing his head into the concrete roadway.

"[They] were behaving like animals … [they] set upon police who were vulnerable on the ground with the suspect and then just started assaulting.

"I've been in the police force for over 30 years and I've seen some really great people out there but I also see the worst of society, and what I've seen on this video and what I've seen through this event is the worst of society.

"If they're going to behave like animals, and it means getting locked up like an animal, that's a matter for the justice system."

Sorry, this video has expired Victoria Police Deputy Commissioner Shane Patton expresses his anger over the attack

The police used capsicum spray in an effort to stop the attack.

"There were several people who rushed to the help of police, and in my eyes they saved them from more injuries," Superintendent Silva said.

One man was arrested at the time, and three others were arrested hours later.

Kayla Potts, 25, of Langwarrin, in Melbourne's south-east, was released on bail. Three other men, aged 26, 27 and 38, are still in custody.

Victoria Police Deputy Commissioner Shane Patton said the investigation was continuing, with at least one man and two women who had not yet been identified.

"There are a number of people in the footage who we haven't yet identified," he said.

"One of those is a man in a brown shirt with a hat on … he's seen being so brave, standing there spitting on our members.

"I can't explain the outrage that I felt when I saw the footage."

'Their head smashed into a gutter'

Deputy Commissioner Patton rejected suggestions the officers were heavy handed in the way they carried out the arrest.

"Police have acted appropriately [and] they've been belted, they've been attacked by a gang of people."

Police released mobile phone video of the attack on the officers in St Kilda. ( Supplied: Victoria Police )

Victorian Police Association secretary Wayne Gatt said the attack was among the most horrific assaults against police he had ever seen.

"I've seen a lot of things, but I literally had to hold my breath watching this one," Mr Gatt said.

"These sorts of incidents will have a lasting impact on these members that goes well after the night's events.

"The broader impact on our membership who witness and see the vicious nature [with which ] these members have been set up on will be quite extraordinary too."

Deputy Commissioner Patton said assaults against emergency service workers were becoming more common.

"Last year we saw nearly 3,000 assaults committed on police officers," he said.

"Each month we're seeing between 10 and 20 police vehicles rammed.

"It's not just police being attacked — it's emergency service workers in general.

"No one comes to work and expects to be lying on a road having their head smashed into a gutter. That is not acceptable."