"South Korea experienced recent high-profile corruption scandals, which led to massive public protests and the swift impeachment and prosecution of the president," the Berlin-based watchdog said in the CPI report.

New Zealand topped the 180-nation list and Somalia ranked rock bottom. The United States came in 16th place, Japan in 20th, China in 77th and North Korea in 171st.

The index evaluates countries based on how corrupt their public sector is perceived to be, using corruption-related data collected by governance and business experts. A score of 70 and above is considered generally clean, while a score of 50 and above means not entirely corrupt.

"Massive corruption scandals had negative effects on perceptions at home and abroad," the Anti-Corruption and Civil Rights Commission said in a statement on the CPI index, apparently referring to the scandal that led to Park's ousting.

It said, however, that a series of fresh efforts to uproot corruption, such as a far-reaching anti-graft law and efforts to root out unfair, connection-based hiring at public agencies and institutions, had positive effects on the index.

The watchdog said South Korea's ranking is still low in light of its international and economic status.

"Anti-corruption and integrity serve as important factors determining a country's competence," the agency said. "We need to make strong, state-led efforts to tackle corruption." (Yonhap)