Iran’s Supreme Leader Ayatollah Ali Khamenei has threatened to exact revenge for the murder of Iran’s high-profile nuclear scientist Mohsen Fakhrizade—a brazen assassination Iran has already blamed on Israel. Fakhrizade led Iran’s nuclear and defense program and was killed Friday in an ambush by five gunman on a rural road. Israel has previously killed an Iranian scientist but hasn’t yet commented on Fakhrizade’s death. Israel’s potential participation in the attack could reignite tension between the U.S. and Iran just as President-elect Joe Biden proposes a plan to return to the Iran nuclear deal that President Trump withdrew from.

Without elaborating, Khamenei said that the first priority following Fakhrizade’s murder is “definitive punishment of the perpetrators and those who ordered it.” “We will respond to the assassination of Martyr Fakhrizadeh in a proper time,” President Hassan Rouhani added. “The Iranian nation is smarter than falling into the trap of the Zionists. They are thinking to create chaos.”