(Reuters) - Phil Mickelson continued his red-hot form as he stormed home with five birdies in his last six holes to stretch his lead to a commanding six shots after the third round of the Phoenix Open in Scottsdale, Arizona on Saturday.

Four ahead of the chasing pack overnight, Mickelson fired a sizzling seven-under-par 64 on another near-perfect day for low scoring at the TPC Scottsdale to tighten his grip on the tournament.

The American left-hander pumped his left fist in celebration after rolling in a 15-footer to birdie the last and post a 24-under total of 189, just one shy of the PGA Tour low for 54 holes.

Compatriot Steve Stricker, with rounds of 60, 66 and 62, set the record at 25-under 188 in the 2010 John Deere Classic.

Birdies at the 13th, 15th, 16th, 17th and the par-four last gave Mickelson a scintillating back nine of five-under 31, leaving fellow American Brandt Snedeker (65) alone in second place at 18 under, a distant six strokes off the pace.

In front of record crowds, Irishman Padraig Harrington fired the day's lowest score with a 63 to sit joint third at 16 under with American Ryan Moore (65).

(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Gene Cherry)