TRAI said it had set a target to achieve 500 million subscribers by the end of 2010, but it crossed the target at the end of September, 15 months ahead of target.

The combined number of wireline and wireless telephone owners in India hit 509.03 million by Sept. 30 from 494.07 million in August, which shows a growth of 3.03 percent, the independent telecom regulator said.

Overall teledensity -- the number of telephones in use for every 100 individuals -- in India has reached 43.50, it said.

Mobile operators added 15.1 million customers in August.

After China, which is described as the world's fastest-growing market for cellular phones with 600 million mobile users, India is the second largest market.

India's private major mobile companies like Bharti Airtel, Vodafone Essar and Tata Teleservices have been announcing innovative offers to attract more and more customers to buy mobile phones.

One of the main reasons for people being attracted to mobile phones is the move by these companies to bring the call rates down to make the phones easier to buy for the poor, who form the majority of India's population of over 1 billion.