Representatives of nearly 120 nations, including dozens of heads-of-state, have convened in Tehran for a meeting of the Non-Aligned Movement.
At the opening ceremony Sunday, Iranian Foreign Minister Ali Akbar Salehi called for NAM leaders to stand against Western sanctions imposed to punish Tehran for its nuclear activities.
Salehi also urged NAM to take a stand against terrorism, especially of the state-sponsored type, and accused U.S., British, and Israeli intelligence services of being involved in the murders of four Iranian nuclear scientists since 2010.
With Iran's support for Syrian President Bashar al-Assad, it is likely that the Syrian crisis will be high on the agenda of the five-day conference.
There have been conflicting reports about whether the leader of Iran's ally Hamas will attend the conference. Iranian news agencies say Hamas political leader Ismail Haniyeh has not been invited, but Haniyeh's office says he plans to attend.
The office of Palestinian President Mahmoud Abbas says he will not attend if Haniyeh takes part.
The Non-Aligned Movement is a Cold War organization that was supposed to provide a forum for countries that were allied with neither the United States nor the Soviet Union. But since the Soviet Union was dissolved in 1991 the group has struggled for both identity and clout.
Some information for this report was provided by AP, AFP and Reuters.