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.
“It’s been pandemonium,” said United Muppetiers podcaster Mike Parrott at Old Trafford. “I don’t think it’s the right thing to do.
“It’s not great. On one side, that’s how protests work in that you need to send a message but it’s also not great.
“Manchester United v Liverpool is the biggest game in English football but we might not even see that now.
“Breaking cameras, breaking glass and rushing the stadium, all these terrible things are not what Manchester United fans want to be associated with.
“They shouldn’t be doing it whatsoever. I don’t think this conveys a message that they want the 50+1 fan ownership, which was the original idea. It hasn’t really worked in my eyes.”
There has been a long-standing campaign against the Glazer family since the Americans’ controversial leveraged takeover of the club in 2005.
Recently, Manchester United boss Ole Gunnar Solskjaer spoke to fans who entered the club’s training ground at Carrington to protest against the owners.
In the wake of the European Super League collapsing, United co-chairman Joel Glazer said the club “apologised unreservedly” but the Manchester United Supporters Trust (MUST) said it had “zero trust in the owners”.
MUST added that Joel Glazer “and his family have shown time and again that their sole motivation is personal profit at the expense of our football club”.
The view from inside Old Trafford
Gary Flintoff, BBC Radio 5 Live producer
In these times, it is quite bizarre to see supporters inside the stadium. Fans broke through at the megastore end, many wearing the green and yellow scarves and baseball caps with their faces covered.
They chanted for the Glazers to get out of their club and many gathered in front of the Sky Sports presentation platform, chanting towards the pundits. One fan threw a flare in the direction of that platform.
A few fans picked up some chairs and threw them as they made their way on to the pitch, and groundstaff had to remove litter from the pitch.
Five or six fans actually made it down the tunnel towards the dressing rooms. The club tell us that dressing rooms weren’t breached and no fans made it inside, but we saw a young man led out of the tunnel and down the pitch. Fans have now been cleared from the interior of the stadium.
The next tricky moment is when the two coaches arrive, because the suggestion is that the fans will do their very best to make a barrier to stop the teams making their way on site here.