At present, the company has the largest 3G footprint in the country with a presence in 13 circles.
"We are delighted to launch 3G footprint across 18 service areas in India, which makes our services available in all major metros in the country, enabling us to target fast growing data market in these circles.
"Together, these circles account for 80 per cent incremental smartphone sales in the country," RCom's Chief Executive Officer for Consumer Business, Gurdeep Singh said in a statement.
RCom's 3G service will now be available in Tamil Nadu, Andhra Pradesh, Karnataka, Kerala and UP East.
The company already has permit for 3G services in 13 service areas, including Delhi, Mumbai, Kolkata, Punjab, Madhya Pradesh, Rajasthan, West Bengal, Himachal Pradesh, Bihar, Odisha, Assam, North East and Jammu & Kashmir.
Sources said RCom has also entered into 3G intra-circle roaming agreement with Aircel to expand its footprint.
However, no immediate comments were received from Aircel.
In April, TDSAT had allowed Airtel, Vodafone and Idea Cellular to provide 3G services using each others spectrum under intra circle roaming agreement.
For the quarter ended March 31, 2014, RCom reported data (mobile internet) customer base of 37.4 million, including 12.9 million 3G subscribers.