Warning: Videos contain coarse language
Supporters broke into the stadium and flooded the field as separate demonstrations took place outside the team hotel and the ground. There were clashes outside Old Trafford when police moved in to try to restore order.
"Following discussion between the police, the Premier League, Trafford Council and the clubs, our match against Liverpool has been postponed due to safety and security considerations around the protest today," read a statement from Manchester United.
"Discussions will now take place with the Premier League on a revised date for the fixture."
The meeting of the northwest rivals was scheduled to start at 11:30 a.m. ET. Manchester City would've been crowned Premier League champions if Liverpool won at Old Trafford.
Images circulated on social media of supporters forcing entry into Old Trafford and then marching onto the pitch. A flare was flung in the direction of a broadcasting team and one protestor was filmed throwing camera equipment.
Supporters seemed to disperse when police appeared in the stadium, but unsavory exchanges followed between fans and law enforcement as thousands of people were still congregated outside Old Trafford.
The starting lineups were released an hour ahead of the scheduled kickoff, but the United and Liverpool squads were unable to travel to the stadium because of the anger inside and outside Old Trafford.
"Our fans are passionate about Manchester United, and we completely acknowledge the right to free expression and peaceful protest," United's statement continued.
"However, we regret the disruption to the team and actions which put other fans, staff, and the police in danger. We thank the police for their support and will assist them in any subsequent investigations."
Red Devils fans are trying to push for a huge shake-up of United's ownership two weeks after the club's involvement in the proposed European Super League was confirmed. The threat of that breakaway competition collapsed after just two days, but it was the latest of numerous grievances supporters have about the Glazer's stewardship.
The Glazers took over the club in 2005 and have since saddled it with hundreds of millions of pounds worth of debt. Despite the financial concerns, huge dividends have been paid out to the club's shareholders. The 2018-19 accounts showed that £18 million was paid out to the five Glazer brothers and their sister Darcie Glazer Kassewitz over that period, according to figures reported by The Guardian's David Conn in 2019.
The long-term disenchantment with the Glazer family has made the sight of gold and green scarves - the colors of Newton Heath, the name under which the club was founded - a common sight around Old Trafford for over a decade. That color scheme was evident in clothing and smoke bombs outside the stadium and The Lowry Hotel, where the team stays before home matches.