Rory McIlroy appeared to raise his middle finger at American fans during the opening day of the Ryder Cup on Friday.

After an exceptional morning for Team Europe, who took a 3-1 lead after the foursomes action, things heated up in the afternoon with the fourballs. 

The home support was expected to be hostile and raucous at Bethpage Black, and US fans ramped up the noise as the day went on.

This led to a flashpoint in the fourth and final match of the afternoon where McIlroy and Shane Lowry were taking on Patrick Cantlay and Sam Burns. 

The European pair were being heckled throughout and after they went two-up on the 11th hole, McIlroy was seemingly triggered by something that was said.

In a clip that has gone viral on social media, as he walked off the green alongside Lowry to significant crowd noise, it looked as if the Northern Irishman then raised his middle finger towards fans. 

GRAPHIC WARNING 

Within the video, McIlroy turned his head and raised his left hand, before he marched on towards the next hole. 

McIlroy's actions generated traction online - with some fans suggesting he was simply waving - and several weighed in on what he had done.

The 36-year-old attracted praise from multiple users as one said: 'Well that's one way to respond to the crowd.'

Another added: 'Guarantee whoever it was deserved it lol,' before a further supporter quipped: 'Don't particularly like Rory but I don't mind it, good to see some fight in him.'

An extra user said: 'Love it,' and another added: 'Good man, Rory.'

However, others criticised his actions. 'Means we (Team USA) are getting under his skin,' one said, as another commented: 'He should chill.'

McIlroy, whose fourball game went on to finish all square, was being cheered on by wife erica stoll, who was leading WAGS of both sides in watching their partners in action. 

Stoll was wearing a straw colored hat and blouse and was seen with golf jewelry on - including a Patek Philippe Nautilus watch.

The hostile atmosphere in New York has been much talked about ahead of this year's Ryder Cup with European captain Luke Donald exposing his players to crowd abuse via virtual reality headsets to prepare his team. 

Donald also employed actors to heckle players with the hope of desensitising his team when it happens over the weekend. 

Speaking about his tactics earlier this week, Donald had said: 'I think my job as captain is to prepare the guys for every scenario.

'Obviously there's a bunch of us in our team that have experienced away crowds – maybe not New York – and we've certainly talked about it as a group, what you've learned, what you think you might have done well, what you think you might have changed.

'The crowd factor is certainly one aspect that I've been looking at but I've been trying to look at this from a very different angle and that's just one element of the preparation that's going into kind of making sure that these guys are ready.

'When we came up with that idea, it was just one idea in a multitude of ideas to get these guys ready.

'At the beginning of a qualification you expect there to be a bunch of rookies that have not played a Ryder Cup before but we actually have a team that has quite a lot of experience being together.'

McIlroy had earlier won his foursomes clash alongside Tommy Fleetwood on Friday morning, with the pair beating Collin Morikawa and Harris English 5&4.