Section 5(3)(b) in The Foreign Exchange Management (Borrowing And Lending In Rupees) Regulations, 2000
(b)where the investment is made out of funds held in Non-resident Special Rupee (NRSR) account, the interest on such Non-convertible Debentures (NCDs) shall also not be repatriable outside India; and the maturity proceeds and interest on such debentures are credited only to the Non-resident Special Rupee (NRSR) account of the investor.