Israeli embassies around the world have increased their level of alert, Israel’s N12 News reported. According to the media outlet, Jewish communities throughout the world were also advised to stay vigilant.

The report comes as Iranian Supreme Leader Ali Khamenei strongly condemned the killing of Iranian nuclear physicist Mohsen Fakhrizadeh, calling for the perpetrators of the crime to be punished.

Iranian President Hassan Rouhani on Saturday accused Israel of being behind the killing, echoing Iranian Foreign Minister Mohammad Javad Zarif, who also stated that the murder appeared to have involved Israel. The Israeli authorities have so far made no comment on the scientist’s assassination.

Fakhrizadeh, who was assassinated on Friday night,  headed the AMAD program, which was purported to be a nuclear weapons development project. Iran has repeatedly denied having any military nuclear program, stressing that it only uses atomic energy for peaceful purposes.