MUST said they did not want to stage further protests, like the one which caused the postponement of the home match with Liverpool, and outlined a way forward with a four-point plan.

"Let's be very clear that no-one wants what happened at Old Trafford yesterday to be a regular event," said the letter.

"What happened was the culmination of 16 years in which your family's ownership of the club has driven us into debt and decline, and we have felt ever more sidelined and ignored.

"After 16 years not one member of the Glazer family has ever had so much as a conversation with us, the club's Supporters' Trust.

"Yesterday, that frustration reached boiling point. We support the right of fans to protest lawfully and, although we did not personally witness any such acts, of course we do not condone any acts of violence.

"None of us want this to continue. We all have better things to do. So we need to find a way forward."

The cancellation of a game in the world's richest soccer league due to fan protests is unprecedented.

Supporters gaining access to the pitch - before the teams even travelled to Old Trafford - was even more startling given the strict coronavirus measures in place around the stadium that keep games closed to any spectators.

One of the flares set off by fans was launched into the stands where the Sky Sports television team was already broadcasting more than two hours ahead of the scheduled kick-off.

Although the protest had been announced in advance, the stadium forecourt on Sir Matt Busby Way was still able to be accessed by thousands of fans - many chanting "We want Glazers out" as flares were set off.

The crowd was only dispersed after baton-wielding police and officers on horseback charged fans as clashes erupted under a shower of flying glass bottles about 20 minutes before the game was due to start.

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

Manchester United said in a statement reports that protesters were able to access the stadium and pitch via a gate opened by club staff were completely incorrect.

The club said barriers were broken and doors were forced.

It had no desire to see peaceful protesters punished but was working with the police to identify those involved in criminal activity.

The club will also issue its own sanctions to any season ticket holder or member identified.

Information about rescheduling the game will be announced after discussion and agreement with the Premier League.

Australian Associated Press