American Tower Corp has agreed to buy a 51 percent controlling stake in Indian mobile mast operator Viom Networks for 76 billion rupees ($1.17 billion) to expand in the world's second-biggest telecommunications market by number of users. American Tower, which already has a presence in the Indian market, will combine its 14,000 communications towers in India with Viom's estate of about 42,200 after the deal -- creating the market's second-biggest mobile mast operator by number of towers. "With a population of nearly 1.3 billion people, rapidly growing smartphone penetration and limited fixed line infrastructure, India's vibrant wireless industry is poised for a sustained period of network investment," American Tower Chief Executive James D. Taiclet, Jr. said in a statement on Wednesday. Indian mobile phone carriers are expanding their high-speed 3G and 4G broadband networks taking it to hinterlands in a country where two thirds of the population is under 35, and income levels are growing rapidly. That has led to an increase in demand for mobile phone masts, which carriers typically lease from specialized tower operators such as Viom. Reliance Jio, the telecoms venture of India's richest man Mukesh Ambani, that is building India's biggest 4G network has signed pacts with Viom and American Tower among others to lease mobile masts. Viom's majority owner Indian mobile phone carrier Tata Teleservices will see its stake diluted to about 34.5 percent from the current about 54 percent after the sale to American Tower, Viom Chief Executive Syed Safawi said in a phone interview. SREI Infrastructure Finance that owns about 18 percent of Viom along with its associates will sell the stake for 29.52 billion rupees, it said in a statement, adding the money will help cut its debt and improve profits. Singapore state investor GIC [GIC.UL] and Oman Investment Fund will also sell their stakes in Viom. American Tower may buy or may be required to buy all or part of the outstanding 49 percent in Viom, it said. Viom generated about 50 billion rupees in rental and management revenue and 21 billion rupees in gross margin for the three months to June 30, American Tower said. It had outstanding debt of 58 billion rupees as of end-September. Indus Towers, a joint venture of India's three top mobile phone carriers, is India's biggest telecommunications tower company with more than 117,000 towers. Bharti Infratel Ltd, a unit of top cellular carrier Bharti Airtel and the only publicly traded Indian telecoms tower operator, owns 42 percent of Indus. Fourth-biggest Indian mobile phone carrier Reliance Communications is also looking sell a stake in its tower unit and sources had told Reuters in July that American Tower was among the potential suitors. Credit Suisse advised Viom and its shareholders for the deal, while American Tower was advised by Evercore and Kotak Investment Banking.