Klaasen shared an extraordinary fifth-wicket partnership of 222 off only 94 balls with David Miller (82*) as South Africa piled up 416-5, their fifth-highest total in ODIs.
Klaasen struck 13 fours and 13 sixes before being caught on the boundary off the last ball of the innings.
A run spree of such magnitude did not seem likely as accurate Australian bowling and a slower than usual Centurion pitch saw South Africa make relatively sedate progress on a ground known for high scoring.
At the second drinks break, the total was 157-3 off 32 overs.
The acceleration started with a stand of 74 off 57 balls between Rassie van der Dussen (62) and Klaasen.
It went into over-drive when the left-handed Miller joined Klaasen and hit the second ball he faced, from leg-spinner Adam Zampa, for six.
Miller’s 82* came from 45 balls and included five sixes and six fours.
HEINRICH KLAASEN IS FIGHTING DOWN AT SUPERSPORT PARK ?
The South African batsman makes 153* off 77 runs and he doesn’t look to be stopping!
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Zampa was hammered for 113 runs off his 10 overs, Marcus Stoinis conceded 81 runs and Josh Hazlewood and Nathan Ellis went for 79 apiece.
It is a must-win game for the Proteas, with Australia leading the five-match series 2-1.
© Agence France-Presse
