Rory McIlroy swore at raucous Ryder Cup fans on Saturday (Sep 27) before extra security was deployed to monitor rowdy galleries during the Europe star's afternoon four-ball match alongside Shane Lowry as tensions reached fever pitch.In his morning foursome match with Tommy Fleetwood, McIlroy - who on Friday had flipped the middle finger to hecklers - used an obscenity as he told noisy fans to "shut up" as he prepared to play a shot.Later, McIlroy was forced to back off a putt by a heckler on the fourth hole in his four-ball match with pal Lowry, a move that drew of chorus of boos and prompted McIlroy to ask a rules official if anything could be done about over-the-top annoyers.As the abuse from spectators continued, extra security staff appeared to have been brought in to keep a watchful eye over the match at Bethpage Black, where McIlroy and Lowry beat Justin Thomas and Cam Young 2-up."It was a really challenging day," McIlroy said. "I'm going to sleep well tonight."Lowry, who took plenty of insults himself, helped top-target McIlroy get through it all."We knew what we were going to get coming here," Lowry said. "It was a very tough day. Being out with Rory doesn't make it any easier. I think he's getting the brunt of it."But I think we dealt with it very well."Speaking after his and Fleetwood's morning 3&2 victory over Harris English and Collin Morikawa, McIlroy said while he had been expecting a partisan atmosphere, some of the crowd behaviour had crossed a line."I don't mind them having a go at us. That's to be expected. That's what an away Ryder Cup is," McIlroy said Saturday. "Whenever they're still doing it while you are over the ball and trying to hit your shot, that's the tough thing."Between shots, say whatever you want to me. That's totally fine. But give us the respect to let us hit shots and give us the same chance that the Americans have."As Europe stretched its lead over the United States, McIlroy became the focus of most of the remarks and insults from the crowd, from the creative to the mundane.