Louis Oosthuizen and Paul Casey are among a congested chasing pack but it is a pair of amateurs who lead the way after round one of the Australian Open.

Japan's Takumi Kanaya, who four years ago shot 85 at the same course, and Chun An Yu of Taiwan each signed for rounds of 65 to lead at six under par in Sydney.

Both players noted just one bogey in their respective rounds to take a two-stroke lead from Matt Jones, Daniel Nisbet and Dimitrios Papadatos.

Oosthuizen and Casey are lurking in a pack of 15 players all three shots off the pace at three under.

South African Oosthuizen went blemish free through his 18 holes, while Casey was also without a bogey on his card having birdied the ninth and made eagle at the par-five 14th.

It was a day to forget for home favourite Adam Scott, though, as the 2009 champion went four over and faces a battle to make the weekend.