Japan-based NTT DOCOMO  said it will invest Rs 800 crore in India''s Tata Teleservices Ltd (TTSL) which the latter will use to expand the coverage as well as strengthen the quality of the 3G network.

The additional investment is part of DOCOMO's ongoing strategy to expand its business presence and revenue sources in India's rapidly growing mobile market, NTT DOCOMO said in a statement.

"DOCOMO plans to newly invest approximately Rs 800 crore, based on its current 26 per cent stake in TTSL. Payment of one portion of the funds has been made so far, and the rest of the investment is scheduled to be completed in May," the company added.

According to the sources, TTSL was planning to raise Rs 3,000 crore through rights issue that would be subscribed by major shareholders, including DOCOMO.

However, when contacted the company spokesperson declined to comment on the rights issue and said that fund raising was an ongoing process.

TTSL is expected to use the capital to expand the coverage as well as strengthen the quality of the 3G network it launched in November 2010, responding to increasing market competition for new customers, the statement added.

In 2008, NTT DOCOMO, TTSL and Tata Sons Ltd, the prime promoter for Tata companies including TTSL, had entered into a strategic alliance in India, under which DOCOMO had acquired 26 per cent of TTSL's shares, worth $2.7 billion.

Through a joint business and technology cooperation committee, DOCOMO has provided TTSL special expertise for networks, value-added services and marketing, as well as the 3G mobile service launched in November 2010, it added.