Montgomerie joined Aussies Aaron Baddeley and overnight leader Adam Scott on seven-under 209 with a patchy two-under 70.

Rumford, second to New Zealander Michael Campbell last year, holds his three-shot buffer over American Jim Benepe and Australians Anthony Painter and Brad King.

Former winner Peter Lonard and 49-year-old Rodger Davis were among a group of four on eight-under 208.

Teenager Baddeley, last week's winner of the co-European Tour's Greg Norman International in Sydney, surged into calculations when he raced up from equal 52nd to joint 10th with a seven-under 65 to lie five shots behind Rumford.

But Rumford stole the limelight with eight birdies in an unblemished round.

He chipped to within two feet at the 16th hole, hit a six-iron to eight feet at the next and smacked a three-iron 150 yards to within three feet of the flag at the last to wrest the advantage.

"The putter fired up for me," he said.

"I was able to capitalise on the shots I did hit close and made a couple of good up and downs out there."

Montgomerie, two shots off the lead when he teed off, remains pleased with his early-season form.

He said: "I am delighted with the way I am playing from tee to green as well as ever, but I just can't score properly yet.

"The way I'm playing I can have a very good round on Sunday, so I'm looking forward to it."