Birmingham's relegation worries deepened as they were beaten 3-0 by Bristol City amid fan protests ahead of the match at St Andrew's.
After Scott Hogan hit the post twice for Birmingham, Nigel Pearson's side exploited defensive mistakes that allowed Kasey Palmer and Antoine Semenyo to score either side of half-time before substitute Callum O'Dowda made it 3-0.
Before the game, there was a minor protest from Birmingham fans driving a van around the city and St Andrew's.
The demonstration was aimed at owners Trillion Trophy Asia and chief executive Xuandong Ren, rather than head coach Aitor Karanka.
Images circulated on social media showing a message reading "Time for a change #bcfc. The fans deserve better. The club deserves better// Dongout //BSHL (Birmingham Sports Holdings Ltd) DO THE RIGHT THING".
Defeat for Blues was their 12th at home in the Championship this season, the joint-most of any team in the EFL along with Southend in League Two.
Blues remain three points above the relegation zone but Rotherham, whose home game against Coventry was postponed, have three games in hand and a better goal difference.
Victory for Bristol City boss Pearson continued his record of never losing to Birmingham as a manager in six meetings.
The visitors created two chances in the first five minutes.
For the first, Blues captain Harlee Dean deliberately ducked out of a header, thinking the ball was going to run to goalkeeper Neil Etheridge.
But it failed to carry enough power and striker Famara Diedhiou was on to it, only to rush and blaze high over the bar when he had time to have taken the ball on further.
Semenyo was next to test the Blues defence, finding himself clean through only to pass when he could have shot and Maxime Colin cleared.
Blues then went desperately close to a breakthrough. Jeremie Bela's mis-hit shot ended up presenting Hogan with an opening, only for the striker to hit the post with a deflected shot.
Hogan hit the post again in the 34th minute, glancing against the foot of the woodwork from Bela's cross.
Bristol City made them pay within 60 seconds. Palmer dispossessed Rekeem Harper in midfield and raced away between Colin and Marc Roberts before drawing Etheridge and calmly sidefooted the ball home.
Palmer went close with the first effort of the second half when his inswinging corner had to be tipped away by Etheridge.
Semenyo made it 2-0 when Etheridge's clearance cannoned off him and bounced into the unguarded net after Kristian Pedersen left the goalkeeper short with a backpass.
O'Dowda scored within 60 seconds of replacing Nahki Wells, rolling the ball past Etheridge after getting the wrong side of Roberts and latching on to Palmer's short pass, to seal a resounding win.
What the managers said...
Birmingham's Aitor Karanka: "No chance [I'll resign]. In my career I never gave up and here isn't going to be the first place. The answer is to keep working in the way I am and to keep trying to do the things I can control. The aim is just to try to organise the training sessions as well as I can, to try to show them to prepare for the games as well as I can and to motivate them as much as I can.
"I tell them they have to do things defensively and attacking-wise, but we finished the game with Sam Cosgrove and Lukas Jutkiewicz up front and we didn't deliver one ball into the box, so it's impossible to score goals. My personality and way of working is to keep going."
Bristol City's Nigel Pearson: "The most important thing is the clean sheet. That's really something I want us to work hard to preserve and to a man, they did it. When you're asking forward-thinking players to do a (defensive) job and do it effectively, it was a very good response.
"We needed to rectify how we played collectively and I thought we did that, both in terms of defending exceptionally well as a side, but also utilising our pace and power. I can go through the side and reflect that everybody did the job they were there to do and I can't ask for a lot more than that."