International inspectors have discovered several tonnes of nuclear material at a previously undeclared site in Syria, the head of the International Atomic Energy Agency (IAEA) announced on Tuesday. Rafael Mariano Grossi, the IAEA's director general, described the find as confirmation of longstanding suspicions about a clandestine nuclear programme run by Syria's former Assad government, and said the material would be brought under international safeguards.

Syria's Foreign Minister Asaad al-Shaibani said his government had voluntarily notified the IAEA on 17 July, declaring the existence of nuclear materials at an undisclosed site outside Damascus. "These materials do not pose a risk," Shaibani said at a joint press conference with Grossi in the Syrian capital, adding that they would remain in Syrian custody while being subject to the agency's oversight system. Grossi praised Damascus's "courageous decision" to come forward, saying it marked the beginning of a new chapter, while cautioning that "a few tons of nuclear material that could be put to bad use" required careful accounting. The precise nature of the fissile material — whether uranium or plutonium, and at what level of enrichment — has not yet been publicly confirmed, as technical analysis is ongoing.

Grossi also visited Deir Ezzor, a city in eastern Syria, where he inspected the site of a suspected nuclear reactor that was destroyed in a covert Israeli air strike in 2007. Israel publicly acknowledged the strike only in 2018. The reactor is widely believed to have been constructed with North Korean assistance and designed to produce plutonium. IAEA inspectors found uranium particles there during a 2024 inspection, and extensive excavation and sampling work is now under way. Grossi also visited a graphite storage site linked to the Deir Ezzor facility; graphite, like natural uranium, is a material used in certain nuclear reactor designs.

The developments come amid reports, first published by US outlet Axios, that Washington and the IAEA had reached an understanding with both Syria and Israel — which had threatened military action — to place the nuclear material under international supervision. Israel had been closely monitoring a location known as "Site 99," where the Assad government was believed to have stored material connected to the Al-Kibar nuclear project at Deir Ezzor.

Since President Bashar al-Assad was ousted in late 2024, Syria's new leadership has signalled a clear break with his government's decades of nuclear secrecy, and Shaibani reiterated that Syria's ambitions in nuclear matters are limited to peaceful energy use. For the wider region, the disclosures are highly sensitive: they confirm that Syria was pursuing a clandestine nuclear programme far more advanced than previously acknowledged, and the process of securing and accounting for the legacy materials will be closely watched by neighbouring states and the international community alike.