Russian Foreign Ministry says 20 employees of the Czech embassy in Moscow have been declared "persona non grata" and they must leave the country by the end of Monday.

In this December 26, 2016 file photo, a Russian flag flying at half-mast is seen above the Moscow Kremlin building in Moscow, Russia.
In this December 26, 2016 file photo, a Russian flag flying at half-mast is seen above the Moscow Kremlin building in Moscow, Russia. (AA)

Russia has expelled 20 Czech diplomats in retaliation for a slew of diplomatic expulsions by Prague and gave the affected Czech diplomats just over 24 hours to leave the country, the RIA news agency quoted the Foreign Ministry as saying.

Moscow made the announcement after the Czech ambassador in Moscow, Vitezslav Pivonka, had been summoned by the ministry. 

"Pivonka had been told that 20 employees of the Czech embassy in Moscow had been declared 'persona non grata," the statement said on Sunday.

The Czech Republic kicked out the Russian embassy staff on Saturday after saying investigations had linked Russian intelligence to the blast in the ammunition depot some 300 km (210 miles) east of the capital Prague.

The Czech Republic said it had informed NATO and European Union allies about suspected Russian involvement in the blast, which killed two people, and the matter would be addressed at an EU foreign ministers' meeting on Monday.

The expulsions and allegations by the Czechs have triggered its biggest dispute with Russia since the 1989 end of Communist rule, when Prague was under Moscow's domination for decades.

The incident also poured more fuel on the worst Russian-Western tensions since the Cold War, stirred in part by Russia's military build-up on its Western borders and in Crimea, which Moscow annexed from Ukraine in 2014, after a surge in fighting between government and rebel forces in Ukraine's east.

READ MORE: Czech government expels 18 Russian diplomats over 2014 blast

US: We stand with Czech Republic

Russia's Foreign Ministry had said earlier the Czech accusations were absurd as Prague had previously blamed the blast on the depot owners, and Moscow would hit back hard.

The United States said on Sunday it stood with the Czech Republic after it expelled Russian diplomats.

"The US stands with the Czech Republic in its firm response against Russia’s subversive actions on Czech soil," said State Department spokesman Ned Price in a statement on Twitter.

"We must act firmly in response to Russian actions that compromise the territorial integrity, energy security, or critical infrastructure of our allies and partners." 

The 2014 blast

Czech Interior and acting Foreign Minister Jan Hamacek said on public television investigators believed the 2014 blast was meant to target an arms shipment due to leave the depot, and to occur after it was gone, likely to Bulgaria.

He said police had later identified two suspects as the same Russian military intelligence officers - Alexander Petrov and Ruslan Boshirov - wanted by Britain for the poisoning of former Russian spy Sergey Skripal and his daughter with the nerve agent Novichok in the English city of Salisbury in 2018.

Petrov and Boshirov are believed to be aliases used by the Skripal's attackers, who remain at large. The Kremlin denied involvement in the incident.

Hamacek said Prague would ask Moscow for assistance in questioning them but did not expect it to cooperate.

READ MORE: Multiple countries expel Russian diplomats over Skripal attack

'Dangerous and malign operations'

The Czech investigative weekly Respekt reported on Saturday that the arms shipment was for a Bulgarian arms trader who was believed to be supplying Ukraine at a time when Russian-backed separatists were fighting Ukrainian government forces in the country's east.

Respekt and Czech public radio named a Bulgarian arms dealer who they said Russian agents had tried and failed to kill. 

News website Seznamzpravy.cz said the arms shipment may also have been destined for Syrian rebels.

Czech police said they were searching for two men who carried passports in the names of Petrov and Boshirov and were in the Czech Republic in the days before the arms depot blast.

On Sunday, the EU's executive commission confirmed that the Czech row with Russia would be addressed during a previously scheduled EU foreign ministers' video conference on Monday.

The United States and Britain offered full support to the Czech Republic, a NATO ally, in its dispute with Russia.

British Foreign Secretary Dominic Raab said on Twitter the Czechs "have exposed the lengths that the GRU will go to in their attempts to conduct dangerous and malign operations," referring to Russia's military intelligence agency.

The United States imposed sanctions against Russia on Thursday for interfering in last year's US election, cyber hacking, bullying Ukraine and other alleged malign actions, prompting Moscow to retaliate.

READ MORE: What is known about the poisoning of Russian ex-spy in Britain?

Expansion of nuclear plant

The 2014 incident re-surfaced unexpectedly at a time of deep sensitivity for Czech-Russian relations.

The Prague government is planning to open a tender worth billions of euros to build a new nuclear power station, and security services have demanded that Russia's Rosatom be excluded from bids as a security risk.

President Milos Zeman and other senior officials have been arguing for keeping Russia in the bidding, but the chances of that appeared on Sunday to have diminished significantly.

"The probability is very low that Rosatom will participate in the expansion of (nuclear plant) Dukovany," said Industry Minister Karel Havlicek, who was previously in favour of including Russia.

READ MORE: US kicks out 10 Russian diplomats, imposes fresh sanctions

Source: TRTWorld and agencies