Bulgaria accuses Russia of other bomb attacks on Nato

"Evidence is being collected on the complicity of these six Russian citizens," she noted.

"The collected evidence points so far, with a great degree of credibility, to the conclusion that the aim of the actions of the Russian citizens was to stop the supplies of [ammunition] to Georgia and Ukraine," she added.

"We are in touch with the Czech Republic, to see if there is a Russian connection," between the two cases, she also said.

The first explosion in Bulgaria took place in 2011 at an arms depot in the village of Lovindol.

Two more occurred in 2015 at military facilities in the town of Sopot and a fourth one in 2020 at an arms warehouse in the town of Maglizh.

They were all triggered by remote devices in a "similar" way, Mileva noted.

And there were "extremely well-founded suspicions" that an attempted poisoning of Bulgarian arms-dealer Emilian Gebrev in 2015 was also Russia's work, Mileva added.

The Bulgarian disclosure was met by Russia's usual sarcasm and what-about-ism.

"It is good that we have not been blamed for killing archduke Franz Ferdinand yet, but the odds are that we will be soon," Russian foreign minister Sergei Lavrov said the same day, referring to a figure from WW1 history.

He accused Gebrev of exporting components for landmines, which are banned by international treaties.

"The EU must answer the question that we posed - which comes down to what the EU does to control the adherence of its members to their obligations ... in the sphere of the arms trade," Lavrov said.

Russia, the same day, ejected seven diplomats from Slovakia and the Baltic states.

It did so after the four EU members had expelled seven Russian diplomats in what the Russian foreign ministry called "pseudo-solidarity" with the Czech Republic.

"The fact that it [the Czech attack] happened seven years ago does not decrease the gravity of these acts," EU foreign relations chief Josep Borrell also told the European Parliament on Wednesday.

"This is not about military intelligence: this is about a grave criminal offence," he added, referring to a bomb blast at an ammunition warehouse in the Czech town of Vrbětice, which killed two Czech citizens.

Turning to Russia's war on Ukraine, Borrell said Russia's "pretension" that it was not a party to the conflict "must be debunked".

"We should also stand ready to look into options for additional response [sanctions], should Russia re-escalate", he added.

Some MEPs urged the EU to blacklist pro-Kremlin oligarchs over the regime's human rights abuses, such as the jailing of opposition leader Alexei Navalny, or to halt a Russian-German gas pipeline, called Nord Stream 2, in reaction to events.

But Borrell ruled out both options.

"The human rights instrument [sanctions] that we approved ... does not consider corruption among one of the reasons to be employed. Sorry," he said.

"The European Union does not have the means and tools to decide what to do on Nord Stream 2. It is a matter of private firms and it is a matter of the Germans," he added.

Russia-China axis

Meanwhile, Borrell's officials, the same day, accused Russia and China of sowing disinformation against Western-made coronavirus vaccines, in order to help sell their own drugs.

"Both Chinese official channels and pro-Kremlin media have amplified content on alleged side-effects of the Western vaccines, misrepresenting and sensationalising international media reports and associating deaths to the Pfizer/BioNTech vaccine in Norway, Spain, and elsewhere," the EU foreign service said, citing dozens of examples.

"A disinformation report that has no factual basis is in itself an example of disinformation," the Chinese EU embassy retorted.

Borrell, in his remarks to MEPs, noted that Moscow was seeking a "strategic alliance" with Beijing to reduce its need for Western technology exports and gas and oil imports.

But Russia would have a hard time replacing its European client, he said.

"Economically speaking, Russia is the size of Italy, not much more than Spain," Borrell noted.

"Russia is an 'annuitant' economy ... without this [EU gas and oil money] it would have a real problem," he said.

"There is no one else big enough to replace us," Borrell also said, adding Russia would have to build "a lot of [new] infrastructure" if it wanted to become "dependent" on China instead.