Serbia's prime minister on Tuesday alleged that the wave of mysterious bomb threats that have emptied schools and public venues in the capital was linked to Belgrade's refusal to sanction Moscow over the war in Ukraine.
Emailed threats have been sent to more than 90 schools and venues including the presidency building, bridges, shopping malls, restaurants, Belgrade's zoo and a football stadium.
No explosive devices were found when bomb disposal teams searched the locations on Monday and Tuesday.
Prime Minister Ana Brnabic said, without providing evidence or giving further details, that the hoaxes originated from abroad because of Serbia's stance on Russia.
"We are the only country in Europe that has not imposed sanctions against Russia, and ... these bomb threats are pressure from abroad because of our refusal to impose sanctions," she said in a TV interview.
Interior Minister Aleksandar Vulin said the bomb hoaxes were "a part of special warfare" against Serbia, adding that the police, which fall under his ministry, were investigating.
"The claims of explosive devices are intended to cause panic and inflict damage on our country's economy but the fundamental goal of all attacks is to prevent Serbia from conducting independent policies and force it to take decisions out of fear and under pressure," Vulin said in a statement.
"A special war is being waged against Serbia. Threats are being sent from different addresses in several European states to institutions, media houses, and companies. The attacks on our country have not been launched nor are they being waged by an individual. These are mass, organized, and very expensive hacker attacks from different hybrid warfare centers," the interior minister said.
Serbia, a candidate for European Union membership, is almost entirely dependent on gas and oil from Russia, a traditional Orthodox Christian and Slavic ally. It also maintains close political and military ties with Moscow.
Similar threats have recently been reported from other countries in the region such as Montenegro, Bosnia-Herzegovina and Croatia. It is unclear whether there are connections between the incidents in the individual countries.
In April, Serbian President Aleksandar Vucic accused Ukraine and an unidentified EU country of being behind a series of hoax bomb threats against Air Serbia planes which maintain regular flights to Moscow. Ukraine dismissed Vucic's allegations as "baseless."
Moscow calls its invasion a "special military operation" to rid Ukraine of fascists, an assertion Kyiv and its Western allies say is a baseless pretext for an unprovoked war.