There was a stronger policing presence outside the stadium on Thursday after some fans managed to get inside and stormed the pitch on May 2.
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The protest began on the forecourt outside the East Stand around 6 p.m. BST. A large group marched towards the gate used by the team coaches at around 7 p.m. BST, where they were met by a line of police.
The club confirmed that the Liverpool team bus used a back gate to enter Old Trafford and protestors who attempted to run around the stadium to block the coach were stopped by mounted police and riot vans.
United had also set up beds for players in executive suites so they could sleep while being at the stadium all day.
Greater Manchester Police issued a statement after the demonstrations, adding that two individuals had been arrested.
"We are aware of a protest currently taking place outside Old Trafford football stadium, with a small number of people seemingly intent on disrupting the fixture," the statement said.
"Officers are in attendance to maintain safety while facilitating the right to peaceful protest.
"Two arrests have been made relating to public order offences."
In addition to the scenes outside of Old Trafford, a large group of protesters surrounded Manchester's Hyatt hotel, Liverpool's base for the game, in an attempt to prevent Jurgen Klopp's squad from making the journey to Old Trafford on the team bus.
Protesters in cars blocked roads surrounding the Hyatt, while an attempt was made to deflate the tyres of one of the Liverpool buses. The club had two buses outside the Hyatt to comply with COVID-19 protocols that require squads to be split into two while travelling.
A Liverpool source has told ESPN that the attempts to deflate the tyres were unsuccessful, but that one bus was blocked by protesters.
The source added that the bus was empty at the time as the players had not boarded, with Klopp and his team eventually arriving at Old Trafford 90 minutes before kick-off, having made the journey in different transport.
A Liverpool source told ESPN, however, that the red coaches outside the Hyatt were not decoy vehicles, despite the squad travelling to the stadium in unmarked, black coaches.
United's home game against Leicester City on Tuesday went ahead without incident after a heavy police and security presence along with a "ring of steel" set of barriers around the Old Trafford venue ensured no access to fans, who are barred from the ground due to COVID-19 restrictions.
As part of the protests which stopped the Liverpool game from taking place, fans blocked the exit of the Manchester hotel that is regularly used by the club for the players' pre-game meal, meetings and rest.
Co-owner Joel Glazer has pledged to engage more with fans going forward.
Information from ESPN's Mark Ogden and Rob Dawson, The Associated Press and Reuters was used in this report.