Harris enjoyed his best day of international cricket

It took Pakistan until the third day of the Karachi Test to produce some combative cricket, but South Africa remained in a strong position.

Paul Harris had his first five-wicket haul and Mark Boucher broke Ian Healy's record number of Test dismissals as Pakistan were all out for 291.

The tourists then reached 76-3 at stumps for an overall lead of 235.

That gave South Africa an excellent position from which to force a victory over the final two days.

The morning belonged to Pakistan, who started on a perilous 127-5 in reply to South Africa's 450.

They reached 219-6, losing only Abdur Rehman in the morning.

The lead is like gold... If we can get it to around 320, it's competitive Mark Boucher

Salman Butt, hit by a stomach illness on day two, was batting out of position at seven but playing confidently with his skipper Shoaib Malik.

Left-arm spinner Harris came back into the contest after lunch, however.

He deceived Butt with a quicker ball which the left-hander tried to play on the back foot, only to be trapped lbw for 24.

That ended an 84-run stand with Malik and crucially exposed the tail.

Realising that crease occupation alone was not enough, Malik began to play some big shots.

But having reached 73, he was well out of his crease when another quicker ball turned and bounced en route to Boucher.

When Gul was also stumped the score was 259-9, the wicket giving Harris his five wickets and Boucher a record 396th Test dismissal.

Boucher broke an eight-year-old record when he stumped Gul

Though South Africa needed the second new ball to account for Asif, Danish Kaneria remaining unbeaten on an entertaining 26, they remained in excellent position with a lead of 159.

The complexion of the match changed when the tourists, having got to 41-0 in their second innings, lost three quick wickets.

The impressive Rehman, on debut, had Graeme Smith caught behind and Hashim Amla stumped for a duck to bring him six wickets in the match.

And when Kaneria immediately had Herschelle Gibbs caught close in off a glove, South Africa were 43-3.

The spinners continued to twirl away, but Ashwell Prince and Jacques Kallis repelled them to avert the crisis and re-establish the tourists' superiority.

Boucher said: "The lead is like gold at the moment. If we can get another 100 runs, say a lead around 320, it's something competitive to bowl at."

Harris was even more bullish, saying a lead of 300 might be enough.

"It will be difficult on this wicket to chase and it will be a true test of my skills in the second innings," he said.