The Northern Irishman was seen raising a finger on his left hand as he walked off the 11th green during his afternoon fourballs match.

Rory McIlroy appeared to react to a fan at the Ryder Cup by making an offensive gesture on Day 1 at Bethpage Black.

The Northern Irishman helped inspire Europe to a 5.5-2.5 advantage after two sessions but after being heckled during his fourballs match alongside Shane Lowry, McIlroy could be seen raising a finger on his left hand as he walked off the 11th green.

McIlroy and Lowry had just gone two up against the American pair of Sam Burns and Patrick Cantlay when a video circulating on social media showed him gesturing in the direction of the crowd.

There is no explanation as to what provoked the gesture, with McIlroy enduring a mixed relationship with USA fans.

Luke Donald was asked about the gesture, but revealed he was not aware that it took place, stating: "Sorry I'm not aware of that, I'm proud of the guys, how they handled the situation, tough environment out there."

Lowry was also spotted making an offensive gesture towards the crowd with supporters heard making personal insults at both players.

On the first tee as McIlroy stepped out before his foursomes match, USA supporters could be heard singing: "F*** you, Rory!"

As Day 1 developed, the New York crowd started to become more rowdy, with heckling becoming more common as Europe came under pressure in a more hostile environment than the morning foursomes.

Robert MacIntyre also had a spiky interaction with an American member of the crowd after a comment on his weight on the 17th tee.

McIlroy endured the atmosphere to record a victory with Tommy Fleetwood in the morning foursomes, dispatching Collin Morikawa and Harris English 5&4.

While McIlroy missed a putt on the 18th green to secure another victory, having allowed a 2 up lead through 11 to slip away.

McIlroy had been amicable with rival American supporters in the build-up this week.

McIlroy's wife and daughter are American and he stated that the USA is "the best country in the world", having lived there since 2008 after becoming a full-time member on the PGA Tour.

"Everyone wanted to make it in America," McIlroy recalled a day out from the first day of the Ryder Cup. "It's the land of opportunity. And I still believe it's the best country in the world, and if you come here and work hard and dedicate yourself, you can be or do whatever you want.

"I am unbelievably grateful and lucky that I got to come to America early on. I think success is celebrated here. I think there's a wonderful sense of work ethic. And yeah, I live here.

"My wife is American. My daughter is American. I have a lot of affinity towards this country, and I think everyone that lives here should have that same affinity because it is, it's a wonderful -- it is a wonderful place."

Rory McIlroy appears to make offensive gesture towards the crowd at Ryder Cup