Drones used to attack Ukraine have "conclusively" been linked to a sanctioned Iranian manufacturer, private investigators said.
The brand name Mado appeared on engine parts in the Iranian-made Shahed drones used by Russia, the company Conflict Armament Research said.
Engine maker Mado and its director Yousef Aboutalebi are under western sanctions for their alleged role in the conflict.
Russia has used the Iranian-supplied drones to bombard Ukrainian cities and infrastructure during the 14-month campaign by Moscow's troops.
Two drone engines recently analysed in Kyiv had Mado markings on their spark plugs, researchers said. Other parts had labels that appeared to refer to the MD-550 engine, a Mado model.
Some components had an eight-digit serial number beginning with 100, a pattern found on other Iranian-linked weapons.
The same pattern appeared on missiles fired at Abu Dhabi by Iran-backed Houthi rebels in Yemen in January 2022, the analysts said. Three people died in the attack.
A similar serial number also appeared on missile parts seized by Britain on the way to Yemen.
The analysts said Mado was suspected of copying British and German designs in its manufacturing of drone engines.
They said efforts had been made to hide the supply chain, for example by removing serial numbers.
Unique Mado markings had not been found on drones that were used by the Houthi rebels to attack Saudi Arabia in 2019, researchers said.
"Before CAR’s recent discovery in Ukraine, investigators were confident, but not certain, that Mado had manufactured these engines," they said in a nine-page report.
The new evidence "conclusively shows, for the first time in the public domain, that Mado is indeed the producer of engines found in Shahed-136 UAVs in Ukraine," they said.
Ukraine was on Friday hit by the first major barrage of air strikes for two months.
The UK's sanctions listing against Mado and its director say the company has provided "components and engines" for drones supplied to Russia.
The company was under US sanctions even before the war in Ukraine, because of its alleged supply of engines to the Iranian Revolutionary Guard Corps.
Iran has admitted supplying drones to Russia but said it provided them before the invasion of Ukraine last February.
Britain said Iran had tried to hide its involvement in shipping arms to Yemen despite a UN embargo.
In one case, the misspelling of the word "Netherlands" appeared to give away a missile component as a bad copy.