Bharti Airtel's proposed merger deal with South Africa's MTN by 31 August 2009 exclusivity deadline may run into turbulence with a group of investors asking market regulator Sebi to investigate multiple aspects of the proposed deal. As per reports the Indian Investors Protection Council (IIPC) has written to Sebi chairman C B Bhave, with a copy marked to Bharti Airtel chairman Sunil Bharti Mittal, asking Sebi to investigate if regulations have been breached for exempting MTN from making an open offer to Indian shareholders.