Iran's armed forces are the best defense against "terror" in the Middle East, President Hassan Rouhani said on Tuesday, urging regional countries not to rely on world powers.

"Today, the largest power against intimidation and terror is our armed forces," Rouhani said at a massive military parade in Tehran.

Israeli Prime Minister Benjamin Netanyahu and Russian President Vladimir Putin have agreed on a plan to avoid "misunderstandings" in Syria amid an apparent military build-up by Moscow to support President Bashar Assad.

The two leaders reached an agreement on Monday during talks in Russia, with Israeli media reporting that the discussions involved avoiding clashes between the two militaries' jets over Syria.

France opened a business development office in Tehran on Monday seeking to renew once-strong economic ties with Iran after the July 14 nuclear deal in the face of "fierce competition".

French Agriculture Minister Stephane Le Foll and Minister of State for Foreign Trade Matthias Fekl inaugurated the "Business France" office on a visit with some 150 business leaders that is to run until Wednesday.

Iran plans to buy Airbus and Boeing passenger planes through long-term payment agreements once a nuclear accord with world powers is implemented, the transport minister said.

Iran desperately wants to upgrade its ageing fleet, which has been hamstrung by nuclear-related and other sanctions, making even spare parts precariously difficult to source.

Iran said Monday it independently collected samples at a suspect military site where illicit nuclear work is alleged to have occurred and later handed them to the U.N.'s absent inspectors.

The disclosure that international monitors were not physically present is likely to feed critics of a nuclear deal between Iran and world powers, who have poured scorn on measures used to check if Tehran's atomic program is peaceful.

The head of the U.N. atomic watchdog, Yukia Amano, Sunday visited Iran's controversial Parchin military site that has been suspected of being used for secret nuclear tests, an official said.

"Amano paid a formal visit to Parchin, and visited some workshops about which there has been some false information," said Behrouz Kamalvand, a spokesman for Iran's Atomic Energy Organization.

The head of the U.N. atomic watchdog held talks Sunday with top officials in Tehran about unresolved concerns over previous "possible military dimensions" to Iran's nuclear program.

International Atomic Energy Agency chief Yukiya Amano's visit comes as a December 15 deadline looms for completion of its long-running inquiry into allegations that at least until 2003, Iran conducted research into how to build a bomb.

The head of the U.N. nuclear watchdog will travel to Iran on Saturday for talks on Tehran's nuclear program with senior officials, the IAEA said in a statement.

The discussions between International Atomic Energy Agency chief Yukiya Amano and the "high-level" officials will take place on Sunday, it said, as a December deadline looms for completion of a long-running investigation into Iran's past nuclear activities.

U.S. Secretary of State John Kerry said Saturday that Syrian President Bashar al-Assad must step down, but not necessarily immediately upon reaching a settlement to end the country's civil war.

Speaking after talks in London with British Foreign Secretary Philip Hammond, Kerry said he was prepared to negotiate to achieve a solution but asked whether Assad was.

Air raids by Saudi-led coalition warplanes killed 15 people in Yemen's capital in one of the heaviest nights of bombardment in months, aid workers and witnesses said Saturday.

One rescuer told AFP at least 10 civilians were among the dead.