Idea Cellular tanked 9 per cent to Rs 85 -- its 52-week low on BSE.
Shares of Bharti Airtel dropped 8.99 per cent to Rs 302. Ambani also announced a 'free welcome offer' for Jio customers from September 5 till December 31.
Reliance Jio will offer users data services free for four months, after which it will offer 10 tariff plans starting at Rs 19 a day for occasional users, Rs 149 a month for low data users and Rs 4,999 a month for heavy data users.
At the RIL's 42th Annual General Meeting, the billionaire industrialist said Jio is targeting 100 million users in a shortest possible time.
Moreover, within 45 minutes of Ambani's speech IDEA lost Rs. 2450 crore, Bharti lost Rs.9800 crore of market cap.
Telecom sector stocks cracked 3% during Mukesh Ambani's address at Reliance AGM.
Share prices of Idea and Airtel slashed by around 3% and 4% respectively soon after Reliance Jio was formally launched in Mumbai on Thursday.