Hezbollah has vowed to retaliate against Israel, as has Iran, for the killing in Tehran of the political chief of the Palestinian Hamas group, Ismail Haniyeh.

One of the sources, a senior Iranian security official, said Iran, along with allies such as Hezbollah, would launch a direct attack if the Gaza talks fail or it perceives Israel is dragging out negotiations.

Iran has vowed to "harshly punish" Israel over the assassination.

Abbas Araghchi is a seasoned pragmatist diplomat who was the chief negotiator in nuclear talks between Tehran and world powers from 2013 to 2021.

Many airlines globally are revising their schedules to avoid Iranian and Lebanese airspace while also calling off flights to Israel and Lebanon.

Egypt's civil aviation ministry later confirmed on Wednesday the notice was intended to reduce flight-safety risks in light of a notification it received from Iranian authorities.

Iran and Jordan are also seeking to improve their relations following recent tensions related to Amman accusing pro-Iranian militias in Syria of smuggling narcotics into the country, and its taking part in the interception of Iran's first-ever direct attack on Israel last April.

The assassination has sent shockwaves through the region, raising tensions and prompting vows of revenge from multiple actors.

More details would be released as the investigation advanced, the report said.

Flowers were thrown at his coffin as it moved slowly aboard a truck through throngs of mourners to be buried at the gold-domed Imam Reza shrine, Iran's holiest Islamic site.

The President's helicopter crashed against a mountaintop in the Varzaqan region on May 19.

Somalia reiterated its earlier stand that the long-standing Israel – Palestine conflict can only be resolved by way of the two-state solution.

The claim from IS came as Iran observed a day of national mourning for those killed in Wednesday's blasts.

President Ebrahim Raisi condemned the "heinous" crime as Iran declared Thursday a national day of mourning.

The 41-year-old had been arrested in August on the orders of prosecutors in Tehran for distributing an "illegal song" that challenged "the morals and customs of Islamic society".

Iran has called for a united front among Islamic and Arab nations against Israel amid escalating tensions in the region.

Prince Mohammed told Raisi that Riyadh is "communicating with all international and regional parties to stop the ongoing escalation.

Khamenei said Israel has suffered an "irreparable failure" on both "military and intelligence" fronts.