David Moyes called for West Ham supporters to get behind the team after a 3-0 home loss to Burnley was marred by crowd issues.
After a scoreless first half, Ashley Barnes' opener in the 66th minute triggered the start of the problems inside London Stadium on Saturday.
Chris Wood also scored twice and each Burnley goal provoked pitch invasions by angry fans, with West Ham captain Mark Noble tussling with one spectator, while another planted a corner flag in the centre circle.
Those sitting directly in front of the directors' box chanted their disapproval towards co-chairmen David Sullivan and David Gold, who eventually departed the room.
Moyes was disappointed with the ugly scenes and called on fans to unite as the Hammers, who are just three points above the drop in 16th, battle to avoid relegation.
"I don't think I've been at football games where I've seen that," Moyes told Sky Sports.
"You cannot cross the line and enter the pitch. All I say to all of them is that we need them – we are fighting for the points.
"We didn't do so well for a couple of minutes in the second half, but we needed the supporters with us in another way.
"I ask now that we stick together and make sure we have enough points to still be a Premier League team at the end of the season."
As for the game itself, Moyes felt West Ham paid the price for not taking their chances when they were on top in the first half.
Marko Arnautovic and Manuel Lanzini failed to make the most of one-on-one opportunities before the break, Burnley goalkeeper Nick Pope using his feet on both occasions to deny the duo.
"We missed two or three chances during the first half but we played well," Moyes added.
"Then there were a few minutes of madness that changed the game, even though we never looked under a great deal of threat.
"The stoppages in play didn't help our concentration, but it's down to us. The game changed with those missed opportunities, and we didn't start the second half quite so well.
"It never looked like the way it was going, that's for sure."
