Corrected - Bharti Airtel cuts mobile data prices as new rival Jio looms

(Corrects price in 5th paragraph to 51 rupees from 99 rupees)

MUMBAI (Reuters) - Bharti Airtel Ltd, India's top mobile phone carrier, cut prices of its mobile data services on a special plan on Monday, accelerating discounts in the highly competitive market as the entry of a new rival looms.

Reliance Jio, a unit of Reliance Industries and controlled by India's richest man Mukesh Ambani, is expected to launch commercial fourth-generation telecommunication services in the coming weeks.

Jio, expected to price its services aggressively, is giving away free voice calls and 4G data benefits for three months as it signs up subscribers for testing of its network.

Bharti Airtel, Vodafone India, and Idea Cellular - the nation's top three cellular carriers - have already started cutting prices, which analysts say is aimed at retaining customers with the impending entry of Jio.

Bharti Airtel announced on Monday a new plan offering 1 GB of data at 51 rupees ($0.8) a month for 12 months if a subscriber pays an initial amount of 1,498 rupees. Typically, 1 GB of 3G or 4G data costs as much as 300 rupees.

Last month, all the three operators slashed their prepaid data tariffs, by more than half under some plans. Pre-paid subscribers account for more than 95 percent of Indian mobile telecom service subscribers.

($1 = 67.1522 rupees)

(Reporting by Promit Mukherjee; Editing by Susan Fenton and Adrian Croft)