Rory McIlroy of Northern Ireland poses with the champion's trophy after winning the PGA Championship golf tournament in Carmel, Indiana.

Carmel, Indiana - World number one Rory McIlroy continued his red-hot form when he cruised to his third win in four starts with a two-shot victory at the BMW Championship on Sunday that locked in the elite 30-man field for the Tour Championship.

With a glittering leaderboard featuring six major winners and four players who have held the number one ranking packed into the top 10, McIlroy carded a five-under 67 at Crooked Stick to collect his fourth PGA Tour win of the season.

The mop-topped Northern Irishman finished 20 under par and will head to the September 20-23 Tour Championship in Atlanta as the favourite to walk away with the $10-million bonus that will go to the FedEx Cup points leader.

Former world number one Lee Westwood of Britain and four-times major champion Phil Mickelson of the United States tied for second place on 18 under par.

McIlroy began the day a shot back of overnight leaders Mickelson and Vijay Singh, but was on the move quickly with birdies at the second and fifth before moving top of the leaderboard to stay with back-to-back birdies at nine and 10.

The 23-year-old then pulled away from the field with birdies at 15 and 16 to open up a three-shot cushion with two to play.

Mickelson, who has discovered a rich vein of form in recent weeks himself, tried to keep pace by trimming McIlroy's advantage to two with birdies on 15 and 16.

But a bogey on 17 removed any suspense, allowing McIlroy a leisurely victory stroll up the 18th where he signed off with his only bogey of the day, a small fist pump and winning total of 268.

Mickelson returned a two-under 70 to finish joint second with Westwood who clinched his first ticket to the Tour championship with a three-under 69.

Tiger Woods, chasing his fourth win of the season, carded a four-under 68 to finish in a tie for fourth with Robert Garrigus at 17 under. - Reuters