Thousands of schools in Italy, Britain and Ireland received false reports about mining.
In Italy, more than 300 schools were evacuated after reports of mining, writes Reuters.
According to a copy of the message seen by the agency, the emails were signed as "Mikhail Andropov, leader of the Misogynistan Wilayat."
In Scotland, Northern Ireland and the Republic of Ireland, many schools also received similar email threats, but they turned out to be false and classes were not disrupted.
Sky News reports that more than 300 schools in Northern Ireland, 470 schools in Scotland and 6,300 schools in Italy have received the letters.
Police Scotland said its cybercrime and fraud unit is investigating and working with law enforcement agencies across the UK and internationally.
The name "Mikhail Andropov" also signed threatening letters sent on Friday to media editors in Ireland and Bulgaria, as well as threatening messages against European airlines.
Podfishis.