"As part of our phase-7 expansion plans, we are planning to invest Rs 4,000 crore in mobile network. We will be installing 8,700 mobile towers, of which 50 per cent will be for 3G," Chairman and Managing Director R K Upadhyay said.

He added the network expansion, currently under way, was likely to be completed by March next year.

The company has already placed orders for procuring equipment for the north and south zones and would place a contract for the east zone soon.

The fifth largest by mobile phone subscribers, it had 14.56 per cent market share, with around 97.1 million mobile subscribers at the end of May, according to the Cellular Operators Association of India.