Manchester United's home game against Liverpool was delayed after about 200 fans broke into their Old Trafford stadium to protest against the Glazer family's ownership of the club.
The game was set to kick off at 16:30 BST but was put back on safety grounds.
United fans got on to the pitch to protest and after they were removed, some got back on to it later on.
There also appeared to be a protest outside the hotel where the United players stayed before the game.
Both clubs have submitted their team line-ups for the fixture but neither are yet at the ground.
The Premier League said on its live blog: "After the security breach at Old Trafford, we can confirm the Manchester United v Liverpool match will not kick off at 16:30 BST.
"The safety of everyone at Old Trafford is paramount.
"At present, there is no revised kick-off time. We will update accordingly."
All fans are believed to have been ejected from the ground and a sweep of the stadium is going to take place.
"We are being held while the stadium is cleared," said BBC 5 Live football reporter John Murray, who was in a car park outside the stadium with about 50 other media people.
"Meetings are ongoing inside Old Trafford in one of the dressing rooms to decide what will happen next."
Fans had gathered outside the ground and scores of green and gold flares - the colours of United's first shirts when they were Newton Heath, and of the original anti-Glazer protests in 2010 - were set off at 14:00.
The protests follow United's decision, along with five fellow Premier League clubs, to join the European Super League last month before they all pulled out.
Referee Michael Oliver and former United captain Gary Neville were among those whose vehicles were surrounded as they entered the stadium.
There was no trouble and both were allowed through amid much anti-Glazer chanting.
Supporters are currently not allowed into grounds because of the coronavirus pandemic.
There has been a long-standing campaign against the Glazer family since the Americans' controversial leveraged takeover of the club in 2005.
