Iran believes that Israel and an exiled opposition group used a remotely-controlled weapon to kill top nuclear scientist Mohsen Fakhrizadeh on Friday.

In a speech at Fakhrizadeh's funeral in Tehran, security chief Ali Shamkhani said the attackers "used electronic equipment" and were not present at the scene. He gave no further details.

The Iranian defence ministry initially reported that Fakhrizadeh was shot when several gunmen targeted his car.

Israel has not commented on the claims.

Fakhrizadeh played a crucial role in Iran's nuclear programme in the early 2000s and more recently had been accused by Israel of continuing to help in the secret development of a nuclear weapon.

Iran insists that its nuclear activities are entirely peaceful.

The funeral ceremony for Mohsen Fakhrizadeh was held at the defence ministry in Tehran. His remains were then transferred to a cemetery in the north of the capital.

Iranian state television showed the flag-draped coffin being carried by troops, and senior officials - including Intelligence Minister Mahmoud Alavi, Revolutionary Guards commander Gen Hossein Salami and nuclear chief Ali Akbar Salehi - paying their respects.

Rear Admiral Shamkhani, the secretary of the Supreme National Security Council, told the ceremony that Iranian intelligence and security services had been aware of a plot to assassinate Fakhrizadeh, and that they had even predicted where the attack might take place.

"Necessary improvements were made for his security, but the enemy used completely new, professional and special methods and, unfortunately, they were successful," he said.

He added: "It was a very complex mission using electronic equipment. There was no-one present at the scene."

The admiral said there were "some clues" about the perpetrators' identities, but that members of Mojahedin-e Khalq (MKO), an exiled Iranian opposition group opposed to clerical rule, were "surely" involved, along with "the Zionist regime and the Mossad" - a reference to Israel and its intelligence agency.

The comments came a day after Iran's Fars news agency, which is linked to the Revolutionary Guards, reported that Fakhrizadeh was killed by a "remote-controlled machine gun".

Arabic-language Al Alam TV meanwhile reported that the weapons used in the attack were "controlled by satellite".

In the aftermath of Friday's attack, Iran's defence ministry had said that "armed terrorists" targeted Fakhrizadeh's car in the town of Absard, to the east of Tehran, and that the scientist was fatally wounded during a gunfight between his bodyguards and the assailants.

Pictures on social media showed a road strewn with wreckage and blood, and a bullet-riddled car.

In his own speech at Monday's funeral, Defence Minister General Amir Hatami reiterated Iran's determination to avenge Fakhrizadeh's killing.

"The enemies know, and I as a soldier tell them, that no crime, no terror and no stupid act will go unanswered by the Iranian people," he said.

As head of Iran's Organization of Defensive Innovation and Research, known by its Persian acronym SPND, Fakhrizadeh had carried out "considerable work" in the area of "nuclear defence", the general said.

The government would double SPND's budget in order to continue the path of the "martyr doctor" with "more speed and more power", he added. (BBC)

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