Two minutes after the break, Garry Monk's side doubled their advantage, centre-back Michael Morrison rising unmarked to nod home a Mahoney free kick.

Famara Diedhiou put Bristol back in the game in the 66th minute with a simple tap-in from Matty Taylor's header across goal.

But, despite dominating from then on, the hosts could not force an equaliser and Birmingham moved menacingly to the fringe of the play-off race.

Both sides went close in the early stages. Bristol's Andreas Weimann saw a low shot from the edge of the box pass inches wide after latching onto Adam Webster's pass.

From the resulting 12th minute corner, Birmingham produced a lightning break that ended with Mahoney crossing from the left and Kerim Mrabti seeing his well-struck shot brilliantly saved by Maenpaa.

The visitors went close again moments later with another raid out of defence. Che Adams let fly from 25 yards and his effort bounced down off the crossbar before being cleared.

Birmingham were looking as bright as their yellow shirts and Mahoney was next to test Maenpaa with a shot from distance, comfortably gathered by the Bristol keeper.

Bristol came up with a telling break of their own in the 29th minute, Weimann drilling a pass to Diedhiou inside the box and the big striker shooting over when he should have scored.

Mahoney's goal followed a lull in the action, but was no more than they deserved. Marlon Pack's poor touch inside his own box allowed the opportunity to develop and Maenpaa was given no chance by the deflection.

Johnson made two changes for the second half, sending on striker Taylor and winger Niclas Eliasson. But before he knew it poor defending had gifted Morrison Blues' second goal.

It was almost 3-0 on the hour when Adams broke into the box and rounded Maenpaa, only for his shot to be blocked on the line by Tomas Kalas.

A third Bristol substitute, Jamie Paterson, provided the cross, which Taylor nodded down for Diedhiou to score and with 24 minutes left, Johnson's men were back in the game.

The home side piled on the pressure, but most of their goal attempts came from distance as Birmingham defended strongly to clinch the points.

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