Moody's Investors Service affirmed on Thursday that the Asian Infrastructure Investment Bank's (AIIB) long-term foreign currency issuer rating is at "Aaa". The outlook remains stable.

The affirmation of AIIB's Aaa rating reflects the development of the bank's operational capabilities and governance frameworks, which Moody's has assessed as evolving in a manner consistent with the highest-rated multilateral development banks, said a statement from the international rating agency.

Moody's continues to expect AIIB to maintain strong capitalization despite near-term challenges to the credit quality of some of its current investments, it said.

At the same time, shareholder support will remain steadfast as its membership and, consequently, its capital base expands beyond the levels at its founding in 2015.

"Overall, the rating incorporates the rating agency's assessment of AIIB's current and future creditworthiness as it continues to ramp up its operations over the next five to 10 years," Moody's said in the statement.