A bus allegedly carrying British diplomats expelled by Russia, leave the British Embassy in Moscow, Russia. Picture: Pavel Golovkin/AP

Moscow - Russia retaliated on Friday against a wave of expulsions of Russian diplomats from Western countries by expelling the same number of diplomats from those countries.

Numerous ambassadors were summoned to appear at Russia's Foreign Ministry to receive the order for expulsions from the country, amid a dispute that has devastated Russia's already tense relations with the West.

Earlier this week, the United States, Germany and more than 20 other countries announced that they were expelling Russian diplomats in an expression of solidarity with Britain.

Britain accuses Russia of perpetrating a chemical weapon attack on a former Russian double agent, Sergei Skripal, in the southern English city of Salisbury earlier this month.

The German Foreign Ministry said it was no surprise that Russia implemented a reciprocal measure in reaction to Germany's expulsion of Russian diplomats.

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"We had not taken the decision to expel the Russian diplomats lightly," the German Foreign Ministry said Friday in an emailed statement.

"Our reaction in the Skripal case was necessary and appropriate as a political signal, out of solidarity with the United Kingdom and because Russia has refused to give any clarification of the facts," the statement said.

Britain had already expelled nearly two dozen Russian diplomats following the incident this month. Russia retaliated at the time with a reciprocal number of expulsions.

Then Russia took it a step further on Friday, ordering Britain to reduce the number of staff members at its embassy and consulates in Russia to a level that matches the number of such Russian staff in Britain.

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Britain's Foreign and Commonwealth Office called Russia's order "regrettable, but in light of Russia's previous behaviour, we anticipated a response."

"Russia is in flagrant breach of international law and the Chemical Weapons Convention and actions by countries around the world have demonstrated the depth of international concern," the British statement said.

Russia has adamantly denied any state involvement in the incident and has even suggested that the attack could have been perpetrated by Britain as a provocation.

Britain has said it was most probable that the Russian state was behind the attack on Skripal, who was released from Russian custody in 2010 in a high-profile spy swap.

Russia's Foreign Ministry said Friday that in a reciprocal measure it expelled the same number of diplomats from Albania, Australia, Canada, the Czech Republic, Croatia, Denmark, Estonia, Finland, France, Germany, Ireland, Italy, Latvia, Lithuania, Macedonia, Moldova, the Netherlands, Norway, Poland, Romania, Spain, Sweden and Ukraine.

Russia is also considering measures against Belgium, Georgia, Hungary and Montenegro, the Foreign Ministry said in a statement.

Russia's Foreign Ministry summoned the US ambassador on Thursday to inform him that Russia was expelling 60 US diplomats and closing the US consulate in St Petersburg.

The US announced earlier this week that it was expelling the same number of Russian diplomats and closed the Russian consulate in Seattle.

German Ambassador Ruediger von Fritsch affirmed after his meeting at the Russian Foreign Ministry on Friday that "Germany's interest in having a good relationship with Russia remains. We remain open to dialogue."

"In the face of the grave incident in Salisbury, it is up to the Russian government to do everything it can to provide clarity and transparency and to answer legitimate questions," Von Fritsch told reporters outside the ministry in Moscow.