(Reuters) - Idea Cellular Ltd (IDEA.NS), India's No.3 mobile operator, posted a 69 percent rise in quarterly profit after adding subscribers faster than its competitors and as its data plans attracted more users.

Idea Cellular, the first telecoms carrier to report results for the quarter to end-September, said it earned 7.56 billion Indian rupees ($123.3 million) in its second quarter, compared with 4.48 billion rupees a year earlier.

The result beat the average analyst estimate of 6.65 billion rupees in net profit, according to Thomson Reuters I/B/E/S.

Idea Cellular added about 1.7 million subscribers to its network in September, according to the Cellular Operators Association of India.

Its average revenue per user rose to 176 rupees in the quarter from rupees 164 last year, the company said. Mobile data volume grew 21 percent from the previous quarter.

Net sales of the company rose about 20 percent to 75.66 billion.

Unlike rival Bharti Airtel (BRTI.NS), which has other businesses, Idea is a mobile services company and operates within India, making it a preferred telecoms stock for some brokerages.

Idea is part of the Aditya Birla conglomerate and about 20 percent owned by Malaysia's Axiata (AXIA.KL).

Its shares closed up 4.7 percent at 161.45 rupees on Monday, before the release of its results.

(1 US dollar = 61.3050 Indian rupee)

(Reporting by Nivedita Bhattacharjee in Mumbai; Editing by Prateek Chatterjee)