Japan is a "natural and indispensable" partner for India in the economic, defense and technology fields, Indian Prime Minister Manmohan Singh said Tuesday in Tokyo while also urging Japan Inc. to increase investment in his country.

"India needs Japanese technologies and investments. In turn, India offers increasing opportunities" for Japanese companies, Singh said in a speech hosted by the Japan-India Association and other groups.

Singh, in Japan since Monday on a four-day visit, stressed that the two countries can deepen cooperation in maritime security, pointing out that India's navy and the Maritime Self-Defense Force have started holding joint exercises.

During the event, Singh presented the prestigious Padma Shri Award to Noboru Karashima, a professor emeritus at the University of Tokyo and a leading authority on Indian history and languages.

The Padma Shri is one of the Indian government's highest awards for civilians. The 80-year-old Karashima was unable to attend the award ceremony in New Delhi in April because of ill health.

On Wednesday, Singh is scheduled to meet with Prime Minister Shinzo Abe. They are expected to agree to resume talks on a nuclear cooperation pact that would allow Japanese companies to export nuclear technology to India for peaceful purposes.

Earlier Tuesday, Singh attended a luncheon with leaders of Keidanren and other business associations.