Telecom regulator TRAI has sought information from leading service providers on their bilateral agreements for entering into 3G roaming pacts, to ensure that there is no violation of licence terms and conditions.

"TRAI is investigating into 3G roaming agreements of telecom operators," a source in the regulator body said.

The watchdog is looking at as to how these companies are selling their 3G spectrum services under the agreement, TRAI sources said.

Earlier, Department of Telecom (DoT) had also raised doubts over 3G roaming pacts of companies, which are not having 3G services on pan-India basis. The pacts help them reduce cost.

In July this year, in an effort to reduce cost and offer pan-India 3G services, Vodafone, Bharti Airtel and Idea Cellular had started sharing their networks to provide seamless service to their customers.

These companies had entered into a bilateral roaming agreement, both inter and intra circle, to provide 3G services to customers in the circles where they can not build their own 3G network as they do not have the licence, in order to bring a pan-India experience of 3G services to their users.

Airtel, Aircel and Reliance Communications each owns 3G spectrum licence in 13 of the 22 telecom circles, while Vodafone has it in 10 circles and Idea and the Tatas in nine circles.

Bharti Airtel had bagged 3G licence for Delhi and Mumbai metros besides states like Andhra Pradesh, Karnataka, Tamil Nadu, Uttar Pradesh (West), Rajasthan, West Bengal, Himachal Pradesh, Bihar, North East, Jammu and Kashmir and Assam.

Idea Cellular holds 3G spectrum for 10 telecom circles — Maharashtra & Goa, Gujarat, Andhra Pradesh, Madhya Pradesh & Chhattisgarh, Himachal Pradesh, UP (East) UP (West), Punjab, Haryana and Kerala.

Vodafone Essar had acquired 3G spectrum in 10 circles including Delhi, Mumbai, Chennai, Kolkata, Maharashtra, Gujarat, Tamil Nadu, Haryana, Uttar Pradesh (E) and West Bengal.