According to the OCCRP investigation, Mkhwebane received a payment of more than $5,000, which was paid into her FNB account in June 2014.
"Adv Mkhwebane would like to place on the record the fact that she heard for the first time from the OCCRP last Thursday that she had been flagged. HSBC has never brought this flagging to her attention and she has absolutely no links with the Guptas," Segalwe said.
He said Mkhwebane has been a target of "dirty tricks" since she started investigating "powerful people" - but did not go as far as naming them directly.
"This is yet another example of the onslaught," said Segalwe.
He said this was one of a number of claims that formed part of an "orchestrated campaign and concerted efforts in political circles, civil society and the media, to discredit her merely because she has been able to muster enough courage to hold those seen as untouchable to account".
"She will not be discouraged. Instead, these attacks give her strength to discharge her functions with renewed vigour, without fear, favour or prejudice," said Segalwe.