The defeat left Newcastle second bottom of the Premier League and winless after their opening eight games of the campaign.
Newcastle said the process of recruiting a new head coach is under way.
Graeme Jones will lead the team on an interim basis, starting with Saturday’s trip to Crystal Palace.
“I am grateful to everyone connected with Newcastle United for the opportunity to manage this unique football club,” said Bruce, who guided the club to 13th and 12th- place finishes in his two years in charge.
“I would like to thank my coaching team, the players and the support staff in particular for all their hard work. There have been highs and lows, but they have given everything even in difficult moments and should be proud of their efforts.
“This is a club with incredible support, and I hope the new owners can take it forward to where we all want it to be. I wish everyone the very best of luck for the rest of this season and beyond.”
In a statement prior to Sunday’s game, Newcastle director Amanda Staveley said the club wanted to be “patient and considered” in their approach and that “change doesn’t happen overnight”.
Staveley is a chief executive at PCP Capital Partners, who are part of the investment group, along with the Public Investment Fund (PIF) and RB Sports & Media.
