Johnson has South Africa reeling

- Scorecard

Left-arm pacer Mitchell Johnson's brilliant spell of bowling helped Australia make a strong comeback and seize the initiative by the end of Day 2 in the first Test against South Africa at the WACA in Perth on Thursday.

Johnson registered his best figures in Test cricket as he claimed seven for 42 to leave South Africa reeling at 234 for 8 at close.

Jacques Kallis and AB de Villiers scored 63 each, adding 124 runs for the fourth wicket, before both were caught behind off Johnson in successive overs, resulting in a collapse.

The 27-year-old's juggernaut continued rolling as he claimed five wickets for just runs in four overs as South Africa lost the advantage after being comfortably placed at 234 for 3 at one stage.

Opener Neil McKenzie fell quite early for 2 when he was caught by Jason Krezja off Johnson, but captain Graeme Smith (48) and Hashim Amla (47) added 90 runs before both fell in quick succession.

The rest of the batsmen failed to counter Johnson's swing and pace as the visitors lost wickets at regular intervals.

Earlier, Australia's last two batsmen continued frustrating the South African bowlers with a gutsy batting display in the morning session.

Jason Krezja, playing in only his second match, was unbeaten on a valuable 30, helping Australia post a respectable 375 in their first innings.

Makhaya Ntini claimed the final wicket, that of Peter Siddle (23), to finish with respectable figures of four for 72.