It also upgraded Hong Kong's foreign-currency bank deposit ceiling from A1 to Aa3, with a positive outlook.

Mr Tang suggested that the decisions show international recognition of Hong Kong's improved public finances and growth prospects.

"Hong Kong has now achieved AA-category ratings by all major international credit rating agencies. The latest ratings are also the highest that have ever been assigned to Hong Kong. The Moody's upgrade is a major breakthrough as it has allowed Hong Kong's rating to rise above that of the Mainland by more than one notch," he noted.

Moody's attributed the upgrade to Hong Kong's strong financial position and large positive international investment position, showing that Hong Kong has a degree of resilience to any potential shocks emanating from the Mainland.

The ratings agency further argued that the large foreign assets held by Hong Kong residents could help Hong Kong weather potential economic or financial shocks.

It added that the upgrade was prompted by its belief that the foreign currency bond rating should be in line with the local one.