Derrick Williams hit the woodwork in stoppage time but, although Rovers stretched their unbeaten run to eight, they will see this as another missed opportunity to make up ground on the top six after a second straight home draw.

The Blues have won just once in their last eight games, but this fightback means they registered a first point in four matches.

Boss Tony Mowbray made six changes, including a return for Lewis Holtby in place of Bradley Dack, while Blues manager Pep Clotet made five changes of his own in a bid to halt a run of three straight defeats.

Both sides had early chances in a disjointed first half. Sam Gallagher lashed a half-volley over after a lovely pass from John Buckley, before Darragh Lenihan was deceived by a long ball that allowed Mrabti to race clear, but his effort from a tight angle was turned behind by Christian Walton.

Opposite number Connal Trueman produced a sensational reflex save on the half hour when Holtby's teasing cross was turned goalwards by visiting defender Harlee Dean, and the stopper's quick reaction reprieved his captain.

Lukas Jutkiewicz spurned a glorious chance before the break, diverting a free header over, before Trueman was in action again, saving a low, 20-yard Armstrong drive.

Birmingham fell behind 10 minutes after the restart but only had themselves to blame as Harding's ill-judged mis-timed tackle brought down Gallagher and gave referee Robert Jones an easy decision to award a spot-kick.

Armstrong did the honours, slamming the ball into the bottom-left corner for his sixth goal of the campaign.

In the season of giving, it was Blackburn's turn eight minutes later, when Bell's outstretched leg upended Jacques Maghoma.

Mrabti stepped up and sent Walton the wrong way, placing the ball into the right corner.

Neither side could grab the initiative, though. Joe Rothwell forced a fine save out of the impressive Trueman, before both sides had good chances in time added on.

First, Williams saw his header thunder against the crossbar, before Birmingham's Kristian Pedersen somehow engineered space to let fly with a shot from the edge of the area which was off target as the points were shared.