* Nazir Patel to replace Nisbet as finance director on Oct 1
* Nisbet will remain part of Bharti transaction team
* Shares down 0.3 percent
By Gugulakhe Lourie and Rebecca Harrison
JOHANNESBURG, June 29 - Africa's biggest mobile operator MTN Group <MTNJ.J> said finance director Rob Nisbet had resigned, raising concerns he may not be in favour of a proposed tie-up with India's Bharti Airtel <BRTI.BO>.
MTN said on Monday that Nisbet, who joined the company in 1995 and is widely respected by investors, will remain part of the team working on a proposed $23 billion cash and share swap deal with Bharti Airtel and will remain an executive director until the end of September. [nLR511040]
Nisbet will be replaced on Oct. 1 by Nazir Patel, who joined MTN in 2005 and has been responsible for group financial management and accounting, and has participated in several acquisitions.
MTN shares were down 0.3 percent at 119.51 rand at 1140 GMT, lagging a firmer JSE Top-40 index of blue-chip stocks <.JTOPI>.
"Nisbet might not have liked the deal and you could even see it in the timing of the resignation, just before the exclusivity period expires," said a Cape-Town based telecoms analyst who did not want to be named.
Nisbet, who has steered MTN through several major acquisitions to help build it into Africa's biggest operator, was not available for comment
MTN and Bharti revived merger talks last month and have agreed to hold exclusive negotiations until July 31. The companies are discussing an initial $23 billion cash and share swap, with a view to an eventual full merger.
Several major MTN shareholders have said they would reject a tie-up based on terms unveiled so far and others are unsure about the deal.
"I think it's a little bit premature, maybe by a year or two," said Irnest Kaplan of Kaplan Equity Analysts, adding the resignation was a negative because Nisbet is one of MTN's longest-standing top managers.
"It's not a train smash and it's not an absolute problem because they have got capable people and Patel is a good guy."
A Cape Town-based fund manager said the timing was odd.
"Although he says he will stay through to see the deal, maybe he is not happy with the transaction or something around the way MTN is trying to aggressively acquire something."
The fund manager said Nisbet might be having "deal fatigue" and did not want to go through another big transaction taking a lot of time and energy.
MTN also said Karel Pienaar, chief technical and information officer, had been appointed managing director for MTN South Africa, replacing Tim Lowry, who will remain head of the South East Africa region. The appointment is effective Aug. 1.