Cries of 'siuu' could be heard throughout much of the home favourite's straight-sets victory over Liam Broady, his first match since a Laver Cup defeat to Stefanos Tsitsipas in September.

The shouts were apparently mimicking Manchester United star Cristiano Ronaldo's famous goal celebration.

There were similar incidents during Andy Murray's battling five-set win over Nikoloz Basilashvili, as the five-time finalist won his first match at the Melbourne major since 2017.

The raucous crowds caused confusion as many observers wondered if Murray and Kyrgios were being booed on court, despite each player also enjoying huge support.

Kyrgios later explained he was not surprised to hear the noise from the stands but was taken aback by how long they persisted.

"It's just a stupid, f***, I can't believe they did it so much," he said after his 6-4 6-4 6-3 victory on John Cain Arena. "They were doing some Ronaldo thing. Ronaldo does it every time he scores.

"It's like... I thought they were going to do it for like 10 minutes. They did it for two and a half hours, like, every point. I don't know why. It was a zoo out there."

Murray had wondered if the crowd was turning on him during his epic 6-1 3-6 6-4 6-7 (5-7) 6-4 victory because he had been targeted during his practice session on Monday.

"Initially, I thought it was [booing] because there were some people booing during my practice yesterday," he said. "I have no idea what for! 

"But then, after a few times, it was like, no, they're doing that, I think it's like 'Siuu' or something that Ronaldo does when he scores. And, yeah, it was incredibly irritating!"

Kyrgios produced some superb if often unorthodox tennis as he booked a second-round clash with world number two Daniil Medvedev, who is the highest-ranked male in the draw following the refusal to allow Novak Djokovic to compete.

The 26-year-old would like to return to John Cain to aid his chances of improving his record against the Russian to 3-0.

"It's going to be a hell of an experience for me," he said. "He's probably 'the' best player in the world at the moment. So I'm pretty excited, I'm excited for that moment. That's why I play the game.

"I feel like those matches still excite me, to go out there and play the best in the world. That was always something I wanted to prove to people that someone like me could do, win those matches.

"I'm not going to go into it with a lot of expectation. I'm going to go out there, have some fun, play my game. I have a pretty set-in-stone game plan of what I need to do to have success.

"As I said, he's probably the best player in the world, he does everything extremely well. He's a hard worker, ticks all the boxes. I'm not going to even think about that now. To play it on John Cain would be – I'm just going to call it the Kyrgios Court – would be fun."