Mills, who was not in the playing XI, was fined 20 percent over and above his match fee after being found guilty of "inappropriate and deliberate physical contact between players" and conduct contrary to the spirit of the game during New Zealand's upset 49-run win on Friday night.
New Zealand captain Vettori was fined a total of 90 percent of his match fee on both charges and Du Plessis was fined 50 percent of his match fee for his part in the pushing incident - which occurred after Mills went onto the field with some drinks after a wicket had fallen at the end of the 28th over of South Africa's innings.
Umpires Aleem Dar and Rod Tucker referred the charges against the three players to ICC match referee Roshan Mahanama, who imposed the sanctions after a hearing involving Mills, the only one of the three to plead not guilty to the charges.
"It was a very important time of a crucial match for both sides but there is never any excuse for deliberate physical contact in international cricket," Mahanama said in a statement. "Vettori and Mills continued to act inappropriately and contrary to the spirit of the game throughout, hence the second charges were laid against them.
"In determining the punishment I have taken into consideration the fact that none of these players has previously been involved in similar breaches of the code."
Mills, who has been sidelined with injuries for New Zealand's last two matches, was ruled out of New Zealand's squad later Saturday for next week's semifinal against either Sri Lanka or England. He injured his thigh in a group match and wasn't expected to recover in time for Tuesday's semifinal.
Mills and the New Zealand team manager had earlier attended a hearing with Mahanama and the umpires after denying the charges. He was fined after Mahanama too submissions from the player, the officials and reviewed video evidence. He had 24 hours to appeal the decision.
New Zealand, South African fined for quarter final clash
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