"India is rapidly becoming the world's fourth-largest economy and is already one of the world markets with the highest prospect for growth. It was clear to us that this was a business opportunity that could not be overlooked," Option Chief Executive Officer Jan Callewaert said in a statement on Monday.

Analysts welcomed the news but said they were more interested in Option's deals on the more sophisticated combination data cards.

Plugged into the side of a laptop, Option's data cards enable users to access the Internet at high speeds without a phone connection on standards such as EDGE, GPRS, WLAN and WiFi.

"We view the inroads in India as important side opportunities for the company, although the impact of sales and EBIT (earnings before interest and tax) should not be overestimated," Dexia Securities analyst Peter van Assche said in a research note.

Callewaert told Belgian financial daily ,i>De Tijd earlier on Monday it was difficult to provide an estimate of how many cards Option would be able to sell in India this year.

Airtel has more than 10.6 million mobile customers.