“MTN has been threatened and attacked by a disappointed competitor and a disgruntled former employee,” he said in a statement.
Dabengwa said MTN had come under increasing public scrutiny after attacks by opponents to its non-controlling 49 percent stake in Irancell.
Claims made by Turkcell in US proceedings had no legal merit and no place in a US court.
“The former employee who is the source of the claims has been shown through the evidence in his deposition not to be a credible witness,” Dabengwa said.
“He is being paid by Turkcell for his role in their legal claims, and has admitted that he is motivated by a grudge against MTN’s former management.”
He said in contrast to Turkcell’s public statements, the former employee’s evidence was significantly discredited in his recent deposition as largely based on speculation, innuendo and hearsay.
Former MTN group CEO Phuthuma Nhleko also denied allegations of bribery on Wednesday.
“No bribes were approved or paid with my consent, or the consent of the MTN Group during my tenure as CEO of MTN,” Nhleko said in a statement.
“The allegations now made by Turkcell are being made inexplicably for the first time in almost seven years after the licence was issued in Iran.”
Nhleko was the group’s CEO and was president of the MTN group of companies for almost 10 years, until March 2011.
Turkcell filed a US4.2 billion (about R35.5bn) civil claim in March, in which it accused MTN of bribing Iranians and South Africans to get the licence, which was originally awarded to Turkcell.
Hawks’ spokesman McIntosh Polela confirmed on Tuesday that the elite police unit was looking into the claims.
“There are allegations. We first did an assessment [to test] the strength of the allegations. After this we decided to do a follow-up investigation,” he said.
Democratic Alliance MP David Maynier said earlier allegations against a high-ranking former MTN executive had emerged.
The executive, who was named by Maynier in his statement, allegedly engaged in “unprecedented corrupt acts” in order to win the mobile operating licence in Iran.
Maynier claimed: “A payment of US400,000 (about R3.38m) was made by MTN to Iran’s former deputy foreign minister Javid Ghorbanoghli for assistance in securing the mobile operating licence.”
Maynier said MTN also allegedly made a payment of US200,000 (about R1.69m) to a South African diplomat — who was also named — to assist with the delivery of a pro-Iran position at the International Atomic Energy Agency.
“MTN financed a trip by Iran’s nuclear negotiation chief Hassan Rowhani to meet former President Thabo Mbeki, to discuss South Africa’s position on Iran at the International Atomic Energy Agency,” Maynier charged.