Iran, Afghanistan and Guinea-Bissau are the riskiest countries in terms of money laundering and "terrorist" financing, according to a study by a Swiss group.

The Basel Institute of Governance, which works with the public and private sector to counter corruption, released its annual Anti Money Laundering (AML) index on Friday.

It ranked 146 countries by how vulnerable they are to financial risk.

"The Basel AML Index measures the risk of money laundering and terrorist financing of countries based on publicly available sources," the report said.

"As there are no quantitative data available, the Basel AML Index does not measure the actual existence of money laundering activity or amount of illicit financial money within a country but is designed to indicate the risk level, i.e. the vulnerabilities of money laundering and terrorist financing within a country."

Sub-Saharan Africa had the lowest performance in the latest index, with five countries in the list of the 10 riskiest.

In the Gulf region, the United Arab Emirates scored the lowest, coming in at number 72 of 146 countries, followed by Bahrain at 81. Kuwait was ranked 90, with Saudi Arabia at 93.

Qatar performed the best in the region, ranked 107 of 146.

Sudan and Taiwan made the greatest improvement in the index, which is in the sixth year since it was started.

Finland was ranked the best, followed by Lithuania, Estonia and Bulgaria.