FILE - In this Tuesday, July 2, 2019 file photo, Bulgarian Prime Minister Boyko Borissov arrives for an EU summit in Brussels. Bulgarian officials say unidentified hackers have stolen the personal details of millions of people from Bulgaria's national revenue agency. Prime Minister Boyko Borissov called an emergency meeting Tuesday, July 16 of all law enforcement services to consider the potential harm to national security. (Geoffroy van der Hasselt, Pool Photo via AP, file)

FILE - In this Tuesday, July 2, 2019 file photo, Bulgarian Prime Minister Boyko Borissov arrives for an EU summit in Brussels. Bulgarian officials say unidentified hackers have stolen the personal details of millions of people from Bulgaria's national revenue agency. Prime Minister Boyko Borissov called an emergency meeting Tuesday, July 16 of all law enforcement services to consider the potential harm to national security. (Geoffroy van der Hasselt, Pool Photo via AP, file)

SOFIA, Bulgaria (AP) — Bulgarian officials said Tuesday that unidentified hackers have stolen the personal details of millions of people from Bulgaria’s national revenue agency and noted a possible Russian link in the case.

Prime Minister Boyko Borissov called an emergency meeting of all law enforcement services to consider the potential harm to the country’s national security. Finance Minister Vladislav Goranov told reporters after the meeting that the hackers behind the breach contacted local media using a mailbox from a Russian domain.

The leak, the biggest in the Balkan country, contains names, personal data and the financial earnings of individuals and companies. According to local media, the hackers have stolen the details of some 5 million of the country’s 7 million people.

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Goranov said the government has requested help from the European Union’s cybersecurity agency.

Speaking to the bTV channel, Interior Minister Mladen Marinov said the attack coincided with Bulgaria’s purchase of U.S. F-16 fighter jets for its air force and that it could likely be motivated by that.

“Organized criminal groups involved in cyberattacks usually seek financial profits, but here political motives are possible. The government decided yesterday to buy F-16 jets,” Marinov said.

The finance minister, however, rejected a possible link to the jet purchase, saying the cyberattack had occurred before the deal was approved.

Bulgarian media, which received an email from the hackers, said it came from Russian mail provider Yandex but demanded no ransom. The email did call for the release of WikiLeaks founder Julian Assange, who is now in a British prison serving a 50-week sentence for jumping bail in Britain and also faces an extradition request by the United States, which seeks him on espionage charges.

Bulgarian media quoted the hackers’ email as criticizing the Bulgarian government and saying “the state of your cybersecurity is a joke.”

It was not clear why the tax agency was targeted but corruption in Bulgaria is widespread. Transparency International says Bulgaria is the most corrupt of the European Union’s 28 nations.