India's Reliance Communication launched a per-second billing plan on Tuesday, days after intensifying price competition pushed sector leader Bharti Airtel into offering a similar scheme.
Reliance Communications, India's second-largest mobile operator, will charge 1 paise per second for all local and national calls, a spokesman said.
Top operators are facing tough competition from smaller rivals, including a venture of Tata Teleservices and Japan's that has grabbed market share with its per-second billing system.
The price war is set to intensify with four firms, including ventures of Norway's Telenor and United Arab Emirates' Etisalat, set to start operations in India this year.
India's has 11 mobile operators currently, and the industry has added an average of 14 million users per month this year.