Iran's president says capitalist excesses caused the global economic meltdown and are un-Islamic.
President Mahmoud Ahmadinejad is among heads of state in Istanbul for a one-day meeting of the Organization of Islamic Conference, a 57-state bloc of Muslim countries.
In an address Monday, Ahmadinejad slammed investments that pay interest, deemed usury by Muslims, and said they had contributed to social and financial problems.
Islamic banks operate according to Shariah law, which bans those investments. Banks instead make money using a system of profit-sharing from returns on approved investments.
In his speech, Ahmadinejad did not refer to Iran's dispute with the West over its nuclear activities.