Pressure is mounting for ownership changes at English Premier League side Manchester United, in the wake of high-profile protests at the club's Old Trafford ground.

Fans broke into Old Trafford and invaded the pitch on Sunday, forcing the postponement of one of the biggest games on the English football calendar, Manchester United against Liverpool.

Although the protest was mostly peaceful, some fans hurled bottles during clashes with police outside the ground.

Two police officers were injured and one of them required emergency treatment for a "significant slash wound to his face" after being attacked with a bottle, the Manchester force said.

"The behaviour displayed today by those at both Old Trafford and The Lowry Hotel was reckless and dangerous," Greater Manchester Police Assistant Chief Constable Russ Jackson said, referring to the hotel where players were staying before the match.

The unprecedented scenes were the culmination of long-running anger against the club's US-based owners, the Glazer family.

Discontent began with a 2005 leveraged takeover of United that loaded debt onto the club, but boiled over last month when the club announced it would be part of the detested European Super League breakaway competition.

Fans groups made their feelings known, saying the time had come to change the structure of football to allow supporters to have more power.

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"On the back of the indefensible ESL proposals, and an "apology" from the Glazers which we do not accept, we need to give fans a meaningful share in the ownership of United and a meaningful voice in how it is run," Manchester United Supporters Trust (MUST) said in a statement after the postponement.

"The government now needs to act. That has to mean a process which results in fans having the opportunity to buy shares in their club, and more to the point, no single private shareholder holding a majority ownership of our football clubs which allows them to abuse that ownership.

Former Manchester United defender Gary Neville, who was inside Old Trafford preparing to commentate for Sky, called on the Glazers to put the club up for sale.

Another former United star, Roy Keane, also spoke about the protest on Sky Sports, saying those involved had chosen their moment:

It's a 'revolution in football', says Wenger

Former Arsenal manager Arsene Wenger weighed in on the protests, saying what happened at Old Trafford was a "revolution in football".

“I would say as a football fan I was against the Super League project because it ignores what makes football great," Wenger said.

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“Football is unpredictable as a sport, but the money and the recruitment of the best players by a small number of clubs has made it more predictable."

He used the example of the Champions League semi-finals, where four of the richest clubs in the world — Chelsea, Manchester City, Paris Saint-Germain and Real Madrid — were the last four in the competition.

"And you come back next year, and you will have the same again. Or Barcelona, or Bayern Munich, or Manchester United.

“On top of that you cannot add even more security and create a league by rights”.

ABC/wires