South Korea's sovereign debt risks fell sharply after rating appraiser Fitch upgraded the country's sovereign rating to "AA-minus," data showed Friday.

According to the Korea Center for International Finance, the country's five-year credit default swap (CDS) premium, or the cost of hedging against losses on sovereign debt, came in at 91 basis points (bps) overnight in New York, down 8 bps from the previous session.

The easing default risk came after Fitch Thursday revised up the country's sovereign rating by one notch to "AA-minus," one grade higher than those for China and Japan, to which "A+" rating was assigned by the agency.

Around 10 days earlier, another rating appraiser Moody's upgraded the sovereign rating by one notch to "Aa3," equaling to those of China and Japan.

South Korea's sovereign debt risks stayed at a high level, surging to 161 bps at the end of last year, but the risks slid at a gradual pace this year amid easing concerns over external uncertainties to 99 bps on Wednesday in the New York trading. The figure was higher than 85 bps for Japan, but was lower than 110 bps for China.