The deal is likely to be valued at between $125 million and $150 million (Rs 810 crore at 54 to dollar), one of the sources said. All the sources declined to be named as they were not authorised to speak to the media before the deal is made public.
Tech Mahindra, which provides IT services to telecoms firms including BT Group and AT&T, has called a news conference in New Delhi "for a strategic business announcement", according to an invite sent to the media.
Billionaire Sunil Mittal's Bharti Group, which controls top telecoms carrier Bharti Airtel, is the biggest shareholder in Comviva. WestBridge Capital, Sequoia Capital and Cisco Systems are the other investors in the company.
Bharti Airtel does not own any stake in Comviva.
The three private equity investors are selling their stake to Tech Mahindra, while Bharti Group is selling part of its holding in Comviva and does not plan to completely exit the company, two of the sources said.
Bharti Group and Tech Mahindra declined comment.
Tech Mahindra, a unit of tractor and sports utility vehicles maker Mahindra & Mahindra, earlier this month agreed to buy Hutchison Whampoa Ltd's back-office call centre business in India for $87.1 million.
Shares in Tech Mahindra traded 1.4 per cent lower at Rs 896.90 at 1.10 p.m. Bharti Airtel gained nearly 2 per cent at Rs 260.
Copyright Thomson Reuters 2012