Spot kicks were required after the fourth round replay had finished 2-2 following extra-time.

Earlier, Schwarzer's fellow Socceroo, Mark Viduka came off the bench to make it 1-1 after City forward David Noble put the visitors in sight of an upset.

"We were probably caught a little off guard," a relieved Schwarzer told Sky Sports. "We were a little sluggish -- but they did very well and put us under a lot of pressure."

And Viduka added: "It was one of those classic cup ties. We had so many chances, we should have buried it and finished it off.

"I couldn't believe it (when City scored their late equaliser). I thought we'd done enough to win the game," the Australian said.

In the day's other fourth round replay teenage striker Chris Martin came off the bench to score the extra-time winner in Norwich's 3-2 win against Blackpool which will see the Championship side away to Premiership champions Chelsea this weekend.

At the Riverside, Boro striker Yakubu Aiyegbeni had an extra-time penalty saved and then hit the post in the shoot-out after the Premiership side and City, who play in League One, English football's third tier, shared four goals just as they'd done in their original fourth round tie at Ashton Gate.

Schwarzer gave Boro an edge when he saved the first kick of the shoot-out from Phil Jevons.

Viduka then made no mistake with his spot-kick but City, after Jevons's miss, were also finding the back of the net during the shoot-out and the score was tied at 4-4 when Yakubu stepped up.

By that stage City keeper Chris Weale had already out-thought the Nigeria striker when he stayed put in the centre of his goal, rather than dive early, to save from Yakubu, who often strikes penalties down the middle. But this one had no power and Weale saved comfortably in the end.

In the shoot-out, Weale didn't have to do anything as Yakubu clipped the right post. But the next penalty saw Schwarzer save from Craig Woodman and, with the tie now into sudden death, Boro youngster Adam Johnson sealed victory.

Bristol, who had been 2-0 down in the first tie, went ahead in the 23rd minute when Andrew Taylor played Noble onside from Alex Russell's through ball and he slid a shot under Schwarzer.

There were only 21 minutes left when Boro drew level when Viduka, on at half-time, headed in England winger Stewart Downing's cross from close range.

In the 95th minute Jamie McCombe brought down Yakubu but he never looked comfortable taking the penalty and Weale saved.

However, it looked as if the forward had settled the tie when he followed up a Johnson shot parried by Weale.

But with three minutes of extra-time left McCombe turned in Scott Murray's cross to set up a shoot-out.

Blackpool who play in League One, the division below Championship Norwich, went into the lead through Michael Jackson's header before Darren Huckerby, who scored in the original 1-1 draw, equalised 12 minutes from time.

Huckerby then put the Canaries ahead in extra-time before Shaun Barker levelled from close range. But with a penalty shoot-out looming, Martin scored.