Rory McIlroy admitted to feeling “a little rusty” after his opening round of 70 on the first day of the Kolon Korea Open in his first tournament back after a month-long break.

The world number six is the star attraction in the OneAsia Tour event but finished his first round three shots behind early leader Jang Ik-jae on one under par after a bogey at the third and double bogey at the 13th created two blots on his round.

It meant the Northern Irishman finished day one in a seven-way tie for 12th place but he could have gone lower had he not put his tee shot in the water on the 13th, as he went on to pick up three shots on the last five holes.

“I just wasn’t very comfortable with the tee shot. I took a long time to get settled over it and then just didn’t make a very good swing,” McIlroyadmitted.

“It was tough, some of the pin positions out there today were brutal, just cut on slopes and very hard to get close to them and when you did get close to them you left yourself very tricky putts.

“I felt I was a little rusty after the four weeks off, but I battled back nicely and to end up under par for the day wasn’t too bad.”

McIlroy has struggled to hit form this year since switching his clubs and had not played since failing to qualify for the 30-man field in the PGA Tour’s final play-off event in September.

The Korea Open marks the start of a month-long tour of Asia for the former world number one that is guaranteed to earn him more than €3million in appearance fees after a disappointing year.

Clubhouse leader Jang claimed birdies on the fifth and 12th with an eagle on the 10th seeing him complete the round in 67, four under par, to finish one stroke ahead of Kang Sung-hoon, Yoon Jung-ho, Hoon Min-kyu and Eric Mina who were tied for second.