Hosts Bradford took the lead in the first half thanks to Garry Thompson's superb volley and both teams created further chances but were unable to take advantage.

The League Two side almost managed to keep their Premier League opponents at bay throughout the second half, but Thomas Vermaelen scored in the 87th minute to make it 1-1 and force extra-time.

The additional periods failed to produce goals and penalties were required to separate the teams, with Bradford prevailing thanks to three misses by the Gunners.

Bradford broke through in the 15th minute with their first real chance, as a free kick caused havoc in the Arsenal box and Thompson volleyed home for a shock lead.

The Gunners came close to an equaliser in the 37th minute after Francis Coquelin struck a shot against the post that bounced away to safety.

Arsenal forward Gervinho then scuppered a fizzing cross in front of an empty goal, a stunning miss that was almost compounded when Nahki Wells sent a shot just wide at the other end.

The visitors increased the pressure after the interval, but a long-range strike from substitute Alex Oxlade-Chamberlain was the best opportunity they could muster in the face of some resolute defence.

It took the Gunners until the 87th minute to find an equaliser and it came thanks to Vermaelen, who was left unmarked at the back post and headed home from close range to draw his side level.

The game then went into extra time, with the best chance falling to Santi Cazorla, who hit the bar with a long shot early in the second period.

With neither side able to find another goal, a penalty shootout was to decide which team would go through to the semi-finals.

Arsenal missed two early spot-kicks in the shootout but Bradford failed to take advantage with a pair of misses of their own, but when Vermaelen stepped up to take his side's final penalty and hit the woodwork, the hosts were celebrating a memorable win.

In Tuesday's other quarter-final, Aston Villa defeated Norwich City 4-1 in an enthralling encounter at Carrow Road.

The hosts took a deserved lead through Steve Morison after a long ball from goalkeeper Mark Bunn, but Brett Holman equalised for Villa with a great strike seconds later.

Despite the match being an even battle, Villa got the all-important goals late on as an Andreas Weimann double and Christian Benteke strike gave Villa manager Paul Lambert a sweet victory over his former employers.