Birmingham's push for Division One promotion took another dent as they were held to a 1-1 draw by a Grimsby side battling to pull clear of relegation.

The Mariners were denied a deserved victory by a goalline clearance and the woodwork as they pressed in the second half to take advantage of Alan Pouton's equaliser from the penalty spot after Andrew Johnson had opened the scoring for Blues.

Chinese international Zhang Enhua, making his last home appearance on loan from Dalian Shide before joining up with the Chinese World Cup squad, saw his second-half shot come back off the frame of the goal.

Birmingham had the ball in the net early on when Dele Adebola fed Nicky Eaden on the right side - but the midfielder was given offside before he crossed low for Johnson to finish the move.

However, Johnson was on hand to net the opener under advancing goalkeeper Danny Coyne as Enhua was caught out by a through ball from Stan Lazaridis in the 10th minute.

Johnson, who had been taken to hospital with a neck injury following a bruising encounter at Stockport, proved a thorn in Grimsby's side all night and he nearly got his second when Paul Groves left Coyne short with a back-pass.

The Grimsby goalkeeper hit his clearance straight at Johnson, but the ball ricocheted out for a goal-kick.

Eaden then shot straight at Coyne, after Johnson had set the midfielder up as Birmingham tried to press home their advantage.

Grimsby's Wayne Burnett needed attention after a challenge by visiting defender Darren Purse and was soon replaced by Pouton.

The early substitute quickly earned a yellow card for a foul on Johnson but redeemed himself with a first-half stoppage-time penalty which gave the home fans something to cheer about.

Jeffreys had forced a save out of Ian Bennett which Purse headed out for a corner - and when Stuart Campbell's corner was handled by Peter Atherton Pouton stepped up to score.

Enhua had a lucky escape early in the second half when he appeared to push over the lively Johnson. But no penalty was given - and neither was it when Birmingham had appeals for a handball against Groves turned down.

At the other end Tony Gallimore fired in a free-kick which deflected off the leg of Curtis Woodhouse - but Bennett got down low to his right to save.

Birmingham twice escaped as first Groves saw his header cleared off the line by Eaden and then Enhua shot the loose ball against the bar.

Grimsby obviously sensed they could claim a valuable victory and had a rush of second-half chances in a match that also brought a glut of bookings - Birmingham's Jamie Pollock and the hosts' Purse, Enhua and substitute Menno Willems all picking up yellow cards.