Bulgarian police said that dozens of schools across the country were ordered to close Monday and Tuesday after receiving email threats of bombs suspected of links to Russia .

"Investigators have come to a major conclusion that these are mixed attacks linked in some way to Russia," Interior Minister Ivan Demirdzhiev said.

The Bulgarian authorities asked for help from the intelligence services of their partners, especially the United States, in an attempt to find out the source of these threats, he added.

The authorities announced that the source of the email threats were Google accounts.

"There are TNT explosives placed in all schools. Your schools will explode soon. I hope you will die," said a message seen by Agence France-Presse.

The prosecutor's office said it was investigating a crime against the republic or terrorism and was working to determine the source of the attacks.

This warning led to the evacuation of dozens of students from schools in the capital, Sofia, and cities located on the Black Sea, Burgas, Varna, and Pleven in eastern Bulgaria, and Pleven in the north, which sparked a state of panic.

No explosives have yet been found in the schools.

In all, 102 explosive threats have been recorded since Monday.

These attacks come days before the general elections in Bulgaria on Sunday, when most polling stations were held in schools.
But the vote will go ahead as planned, unless an actual threat emerges, as confirmed by the interior minister.