Israel assassinated a top Iranian nuclear scientist with a remotely controlled device, the head of Iran’s national security council said on Monday, appearing to contradict earlier official accounts of a roadside ambush, Bloomberg reports.

“The enemy used a completely new, professional and specialised method and technique,” said Ali Shamkhani, secretary of Iran’s Supreme National Security Council, according to the semi-official Tasnim news agency.

“The operation was very complex and used electronic devices, and no one was present at the scene.”

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Officials had originally said that Mohsen Fakhrizadeh, a veteran scientist who worked on nuclear and defense projects, was killed outside Tehran on Friday in a bomb and gun attack.

State-run Press TV reported on Monday that “the remains” of a weapon collected from the site “bear the logo and specifications of the Israeli military industry.” It cited an unidentified person and didn’t provide any evidence to back up the claim.

Fakhrizadeh was buried in northern Tehran on Monday next to the grave of Majid Shahriari, a nuclear scientist who was assassinated in a 2010 operation Iran also blamed on Israel.