Iran is hosting leaders from around the world for a two-day summit of the Non-Aligned Movement, which it hopes will boost its position on the international stage.
The event has already upset Washington after UN Secretary-General Ban Ki-moon announced his attendance.
The US has imposed tight sanctions on Iran because of its nuclear programme.
On the summit's agenda are finding a solution to the crisis in Syria, human rights and nuclear disarmament.
The BBC's Tehran correspondent, James Reynolds, says the meeting gives Iran a chance to fight back Western efforts to isolate it because of its nuclear activities.
The two-day summit, which caps a week of meetings in Tehran, involves delegates and leaders from 50 countries of the 120-member Non-Aligned Movement (Nam).
Those attending include India Prime Minister Manmohan Singh, Egyptian President Mohamed Mursi, Syria's Prime Minister Wael al-Halqi and Qatar's Emir Sheikh Hamad bin Khalifa.
Mr Mursi's arrival in Tehran on Thursday morning has attracted a lot of media attention in Iran with many commentators hailing his appearance.
State television broadcast live pictures of him disembarking from his plane and being greeted by Iran's Vice President Hamid Baqaei.
Mr Mursi's visit is the first by an Egyptian since the 1979 Islamic Revolution, when Iran cut ties with Hosni Mubarak's administration over its signing of a peace treaty with Israel.
The Muslim Brotherhood's Foreign Relations Unit has told the BBC that Cairo's intentions are merely to normalise relations with Tehran, rather than significantly change them.
The UN's Mr Ban arrived on Wednesday and met with Iran's Supreme Leader Ayatollah Ali Khamenei and President Mahmoud Ahmadinejad.
His positive RSVP to Tehran has been described by the US State Department as "strange", but the South Korean has not shied from drawing attention to the Islamic Republic's human rights record.
In a press conference, seated next to the speaker of Iran's Parliament and one of the country's most powerful politicians, he told reporters that he has "serious concerns" about human rights in Iran.
A spokesman for Mr Ban has also said that he wants to address the slow progress in multilateral talks related to Iran's disputed nuclear activity.
The US and many of its allies suspect Iran's nuclear programme is aimed at developing a weapon, but Tehran insists it is strictly for civilian purposes.
A foreign minister's meeting on Tuesday was dominated by criticism of sanctions against Iran and decision-making at the UN.
Iran also hopes to use the gathering to significantly change the balance of international opinion regarding its nuclear ambitions.
Iran is one of the few remaining allies of embattled Syrian President Bashar al-Assad and has been accused by the US of training a militia in Syria to reinforce Mr Assad's forces.
According to his spokesman, Mr Ban urged Ayatollah Khamenei and Mr Ahmadinejad to "really reach out to the Syrian leadership and impress on them the really urgent need to stop the violence".
The website of Ayatollah Khamenei said the Supreme Leader told Mr Ban in their meeting that the solution to the crisis was halting the trafficking of weapons to Syrian rebel fighters.
He said it was "natural" for there to be weapons in the hands of the Syrian government, because it was conducting an official military like any other country.
The Nam was established in 1961 by countries that wanted to counterbalance the dominance of the United States and Soviet Union during the Cold War.
It meets once every three years but its relevance on the international stage has declined significantly since the end of the Cold War and the fall of the Soviet Union.----
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