TURIN, Italy, Sept 15, 2012 (AFP) - Mulroy, sitting only one shot behind overnight leader Richard Bland, started with a birdie at the first and made up for a bogey at the fifth by reeling off three successive birdies in his outward nine.
At the turn he birdied the 10th and 13th holes and finished with another birdie at the last.
Mulroy, who said the Royal Park I Roveri reminded him of courses back home, would receive a huge boost in the event of victory.
"I haven't played so well this year. It would be a big thing to win on mainland Europe, especially with the purse here and the two-year exemption," he said.
But with nine players only four shots off the leading pace, Mulroy faces a big challenge on Sunday.
A day after a second successive 66, 39-year-old Bland picked up one bogey and failed to produce the birdie blitz which, for two days running, had put him in surprise contention.
He is now in a six-strong group which sits four shots off the pace of Mulroy, whose three-round total of 199 gave him a one-shot lead over Gonzalo Fernandez-Castano.
Had Fernandez-Castano not picked up four bogeys his round of 67 -- which included seven birdies and an eagle at the par five eighth -- he may have taken the overnight lead.
"I played well but I had a few unforced errors which cost me a few shots," said Fernandez-Castano.
"But two birdies to finish on the last two holes has put me back in contention and I'm in a great position for tomorrow."
Sitting one shot further behind on 201 are fellow Spaniards Rafa Cabrera-Bello, who shot a 65, and Pablo Larrazabal, who carded a 66.
Alongside Bland at four shots off the leading pace are Italian Matteo Manassero, Welshman Phillip Price, Germany's Martin Kaymer and Frenchman Gregory Bourdy.
Bourdy's round of 70 included two bogeys and only four birdies but perhaps the most disappointed was Marc Warren.
The Scot started the third round only one shot behind Bland but made only three birdies and bogeyed the fourth, 10th and 16th holes on his way to a level par 72 which left him six shots off the lead.
Leading third round scores in the Italian Open at Royal Park I Roveri, Turin, on Saturday (par 72, GBR and IRL unless stated):
199 - Garth Mulroy (RSA) 66 67 66
200 - Gonzalo Fdez-Castano (ESP) 68 65 67
201 - Rafael Cabrera Bello (ESP) 67 69 65, Pablo Larrazabal (ESP) 69 66 66
203 - Richard Bland 66 66 71, Phillip Price 68 69 66, Matteo Manassero (ITA) 69 69 65, Nicolas Colsaerts (BEL) 71 67 65, Gregory Bourdy (FRA) 69 64 70, Martin Kaymer (GER) 70 66 67
204 - Joel Sjoholm (SWE) 64 71 69, Hennie Otto (RSA) 70 67 67, Shane Lowry 70 67 67, Sam Little 67 68 69, Victor Dubuisson (FRA) 66 69 69
205 - Emiliano Grillo (ARG) 68 70 67, Marc Warren 68 65 72, Anders Hansen (DEN) 70 68 67, Keith Horne (RSA) 66 71 68, Lorenzo Gagli (ITA) 69 68 68, Lee Slattery 65 71 69
Selected:
206 - Thomas Aiken (RSA) 70 67 69, Richard Sterne (RSA) 67 68 71, Bradley Dredge 67 69 70, Graeme Storm 69 68 69
207 - Dylan Frittelli (RSA) 70 67 70
208 - Edouard Dubois (FRA) 67 72 69, Jaco Van Zyl (RSA) 71 69 68, Gregory Havret (Fra) 70 69 69