GSM operators in September added 6.52 million new subscribers in September against compared 5.33 million in the previous month.
The GSM subscriber base stood at 618.28 million at the end of last month.
"The reason for the reverse in September is mainly due to the subscribers addition in states like Kerala, Punjab, UP [East/West], West Bengal, Rajasthan, Madhya Pradesh and North East, where operators like Uninor and Idea are adding good numbers," COAI Director General Rajan S Mathews said.
Subscriber additions had been declining for four months since May in which the addition was below the 10-million mark at 9.53 million for the first time since October, 2009.
In September, Bharti Airtel, the largest GSM player, added 0.94 million users, taking its total subscriber base to 172.78 million, the data released by the Cellular Operators Association of India (COAI) showed.
It had 27.95% market share at the end of September.
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Vodafone Essar, with a 23.45% market share, notched up 0.85 million new subscribers during the month. Its subscriber base reached 144.99 million in September.
Aditya Birla group firm Idea Cellular added 1.74 million users during the month to take its total user base to 100.18 million, while Aircel added 0.60 million customers to take its subscriber base to 59.79 million.
State-owned telecom firms BSNL and MTNL added 0.45 million and 0.03 million new users, respectively, taking their subscriber base to 91.07 million and 5.33 million, respectively.
The COAI data excludes data from Reliance Communications.
GSM (Global System for Mobile Communications) is the most popular standard for mobile telephony systems in the world.
The other technology platform on which Indian telcos offer services is CDMA (Code Division Multiple Access), where players such as Tata Teleservices (TTSL), RCom and MTS are the main operators. These two offer both GSM and CDMA services.