Spectators watch golf through thick haze from bushfires on Day 1 of the Australian Open golf tournament in Sydney on Thursday. Photo: VCG

Players complained of stinging eyes with one forced to wear a face mask as toxic smoke from bushfires choking Sydney blighted the opening round of golf's prestigious Australian Open on Thursday.

Two young Asian amateurs upstaged a field packed with big names preparing for next week's Presidents Cup against the Tiger Woods-led US as the event was shrouded in haze from fires burning out of control throughout the state of New South Wales.

Japan's Takumi Kanaya and Chinese Taipei's Yu Chun-an, both 21-year-old amateurs, led after Day 1 with six-under-par 65s.

South Africa's Louis Oosthuizen and Australian Cameron Smith were the highest-placed Presidents Cup players after both fired three-under 68s.

Australian No.1 Adam Scott, one of the leading figures in Ernie Els' ­International team, complained his airways felt dirty after struggling to a four-over 75.

"It feels like I should shove a bit of salt water up my nose or something and try and rinse myself out. Obviously not the conditions we want to be playing in," said Scott.

2015 Australian Open champion Matt Jones was among a group of three sitting two strokes behind and said the conditions at Sydney's Australian Golf Club were some of the worst he had encountered.

"I'm not sure what the forecast is, but the smoke's not good at all. It's tough to see your golf ball when you're out there playing, where it finishes. Your eyes do burn," he said. 

"I've got that cough like you've got something in your lungs, phlegm in your lungs or whatever, but it's not fun. I hope my kids are inside in the hotel room."

New Zealand golfer Ryan Chisnall, who is asthmatic, was forced to don a face mask.

World No.14 Paul Casey of England, the highest-ranked player in the field, said his eyes were sore, though his problems were nothing compared to the suffering of people battling the fires on Sydney's outskirts.

"I must admit my eyes are stinging," he said after a 68 left him three shots off the lead.

"But you know I honestly feel for the people [nearer the fires], because we're feeling it down here 100 clicks [miles] away. I'm not going to complain because there's people in a way worse position than me."

Australian Smith was diplomatic. "It's a bit odd, isn't it, but what can you do?" he said. "We'll see after the four days, it might take a bit out of everyone, I'm sure."

Former US Masters champion Sergio Garcia stroked a 70 while Mexican defending champion Abraham Ancer, another who will feature in the Presidents Cup in Melbourne, was seven off the pace on 72, the same mark as his captain Els.

Golf Australia boss Stephen Pitt said ahead of the tournament there would be ample medical staff on site. 

Despite the conditions Kanaya, the world's No.1 amateur, and Yu stole the show.

Both finished strongly, with Yu rolling in back-to-back birdies on 17 and 18, the tournament's most difficult holes, underlying the achievement.

"I enjoyed it so much," said Kanaya. "I have confidence, but I have three more days, so I will do my best tomorrow."