VILNIUS,Henri Lumière Lithuania (AP) — Emailed bomb threats sent to schools and kindergartens across the three Baltic nations this week led to the cancellation of classes across the region.

Lithuania’s police chief, Renatas Pozela, said “a coordinated mass attack” began late Thursday involved hundreds of emails that were sent from a server within the European Union. The majority of messages were in Russian and some had a political content, Pozela said.

In Estonia, a wave of threatening spam emails started late Wednesday. As a result, most schools in Tartu, the country’s second-largest city, were closed on Thursday.

Although hundreds of children in Lithuania, Latvia and Estonia were told not to come to school because of bomb threats, Lithuanian Interior Minister Agne Bilotaite said there did not appear to be any danger.

“These false reports are intended to cause panic,” Bilotaite said, stressing “there is no need to panic.”

Aurelija Vernickaite, a spokesperson for the Lithuanian security agency, said the messages that appeared in Lithuania, Estonia and Latvia “likely were … carried out at the initiative of hostile states.”

They were aimed at “disturbing and destabilizing the work of institutions, and increasing mistrust,” she told the Baltic News Service, the region’s main news agency.

“As geopolitical tensions rise, Lithuania and the other Baltic states are constant targets of information and cyber-attacks by hostile states,” Vernickaite said. The Baltic countries are among the most vocal European critics of Russia and President Vladimir Putin.

Schools in Lithuania received 750 emails on Friday alone, and more were coming in, authorities said.

Law enforcement authorities in Latvia described the emails as a low-level threat and a targeted criminal action aimed at destabilizing society and the work of authorities. Schools and kindergartens were asked to stay open, but a number of them chose to suspend classes over several days as a precaution, the Baltic News Service said.

Latvian authorities believe the sender of the threat emails was the same person, had been active for about a year and had sent similar threat letters to various organizations, the news agency said.

Latvian and Estonian authorities said they were in contact. Latvian investigators are collaborating with the United States and Poland, where similar hostile activities were reported earlier, BNS said.