South Korea's national debt to gross domestic product (GDP) ratio fell to one of the lowest numbers among major economies in 2011, the Organization for Economic Cooperation and Development (OECD) said Sunday.

As of the end of 2011, the country's debt to GDP ratio came to 33.6 percent, down 1 percentage point from a year earlier.

The figure is the fourth lowest among the 34 member countries of the OECD after Australia, Luxembourg and Chile. The debt-to-GDP ratio is a key indicator of a country's financial soundness.

Japan posted the highest debt to GDP ratio of 211.7 percent at the end of last year, up 11.7 percentage points from a year earlier, according to the OECD.

South Korea's improved financial stability apparently helped recent decisions by two global ratings agencies -- Fitch Ratings and Moody's Investors Service -- to upgrade the country's sovereign credit ratings by one notch.

In its five-year fiscal management plan, submitted to the parliament on Wednesday, the Ministry of Strategy and Finance said it will bring the debt to GDP ratio to below 30 percent in 2016, further improving the country's financial soundness.

With improving stability in its financial conditions, South Korea's default risks dropped to a 12-month low, according to industrial data.

As of Friday, the credit default swap (CDS) premium for the country's five-year currency stabilization bonds slipped to 84.2 basis points, down 14.6 basis points from the previous day. (Yonhap News)