NEW DELHI, INDIA: Leading Indian mobile firm Bharti Airtel on Friday said it would charge 50 paisa per minute (1 U.S. cent) for local and national calls on its network, heating up competition in a market that already has some of the world's cheapest tariffs.

Local call rates in India now average U.S. 2 cents per minute, and national long-distance calls are priced at about U.S. 3 cents, with variations depending on bill plans and operators.

Bharti Airtel, whose 110 million users account for nearly a quarter of India's mobile subscribers, said more than 95 per cent of its users made local and national calls to another number on its network.

Operators can offer cheaper tariffs within their own network as they do not have to pay interconnection charges which apply if a call is made to another operator's network.

India is world's fastest-growing mobile market with operators adding more than 10 million mobile users a month, and competition has led to drop in tariffs as new entrants try to win subscribers.

Second-ranked Reliance Communications expanded its GSM services this year and offered free call minutes for some months to lure subscribers, leading to record sign-ups.

Sixth-ranked Tata Teleservices recently launched a GSM-based mobile service with a per-second billing plan that helped it post its highest-ever monthly additions in July.