Iran ranked 147th out of 180 countries in a global corruption perception index, a watchdog group said in a report released Tuesday.

The Transparency International report also gave Iran a Corruption Perceptions Index (CPI) score of 25.

A country's score is the perceived level of public sector corruption on a scale of 0-100, where 0 means highly corrupt and 100 means very clean, the report said. A country's rank is its position relative to the other countries in the index. Ranks can change merely if the number of countries included in the index changes, it added.

Therefore, the rank is not as important as the score in terms of indicating the level of corruption in that country, the report said.

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"Countries with high CPI scores generally face fewer violent threats," the Transparency International report said.

"The case of Iran, which has been stagnant on the CPI at its historical minimum of 25 for the past three years, illustrates this point: tensions in the country had been building as a result of the economic crisis, the impact of international sanctions and grievances over corruption," the 2022 report said.

It also said the death of Mahsa Amini in September 2022 served as a catalyst for protests by women's rights activists and frustrated citizens. Amini, an Iranian Kurdish woman, was arrested for allegedly not wearing her hijab correctly. She died in police custody, sparking nationwide protests.

"While the sexist laws and the unjust treatment of women in the country were at the core of the protests, the declining living conditions and corruption in government further fueled the anti-government messaging," the report found. "As summarized by Human Rights Watch, 'In a country with mass repression, unfree elections and apparent corruption and mismanagement, Iran's autocracy rules with all that remains: brute force.'"

At least 520 protesters have been killed and 19,400 others arrested in Iran since the protests began, following Amini's death on September 16, 2022. Iran has also handed down a number of death sentences and has executed at least four people.

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Iran moved up three places, from 150 to 147, in the 2022 ranking, falling below countries such as Uganda (26), Mozambique (26), Madagascar (26), Liberia (26) and Cameroon (26).

The top five on the CPI list are Denmark (90), Finland (87), New Zealand (87), Norway (84) and Singapore (83). The bottom five are Somalia (12), Syria (13), South Sudan (13), Venezuela (14) and Yemen (16).

The annual Transparency International report has ranked 180 countries and territories around the world on a corruption scale since 1995 based on surveys with experts and businesspeople, Agence France-Presse reported.

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The index scores are calculated using 13 different data sources that provide perceptions of public sector corruption from businesspeople and country experts. Sources include the World Bank, the World Economic Forum and private risk and consulting companies, The Associated Press reported.

The organization's mission is to "stop corruption and promote transparency, accountability and integrity at all levels and across all sectors of society."

Some information for this report came from Agence France-Presse and The Associated Press.