Nato today began a series of controversial military exercises in Georgia following an apparent failed uprising at a Georgian army base yesterday and Moscow's expulsion of two Nato diplomats this morning.
Russia said it was expelling Isabelle Francois, the Canadian head of Nato's Moscow information office, and a worker at her office.
The move was in retaliation for last week's expulsion of two Russian diplomats, who had been accused of spying, from Nato's Brussels HQ, Russia's foreign ministry said.
The ministry said it was summoning Canada's ambassador to Moscow.
"The withdrawal of diplomatic accredition in Moscow will be our response," a Russian official told the Interfax news agency. "We are not the ones who initiated such behaviour. We have been forced to act in this way."
Today's Yesterday's exercises involve 15 Nato countries, among them Britain.
The manoeuvres have provoked a furious reaction from Russia, which has described them as "dubious" and a "provocation".
Moscow has also lambasted Mikhail Saakashvili, the pro-western Georgian president.
Yesterday, Saakashvili claimed to have thwarted a Russian-backed mutiny at the Mukhrovani army base near the capital, Tbilisi.
Russia dismissed the claim as "absurd" and suggested Saakashvili "send for a doctor".
Dmitry Rogozin, the hawkish Russian ambassador to Nato, said Nato should cancel the exercises.
"Nato needs to show flexibility and hear our arguments. The worst thing is that this organisation is becoming more and more unpredictable," he said. "Nato's behaviour is not decent, stable or appropriate."
The exercises take place against the backdrop of a growing military buildup on both sides of Georgia's tense and disputed borders with the breakaway republics of South Ossetia and Abkhazia.
Russia has beefed up its military presence in both territories, and last week signed an agreement giving its army full control of border security.
The EU and Nato have strongly protested against the move, saying it is in breach of a peace agreement signed last August by Russia's president, Dmitry Medvedev, and the French president, Nicolas Sarkozvy.
Under the deal, Medvedev promised to pull Russian troops back to their positions before last summer's war over South Ossetia.
Saakashvili's position in Georgia, meanwhile, is increasingly under threat following a series of protests by the country's opposition.
Opposition leaders have dismissed yesterday's apparent army mutiny as a fabrication by Saakashvili designed to discredit his internal enemies.
The opposition accuses him of mismanaging the South Ossetia war and wants him to quit.
Underlying the simmering conflict with Nato is Russia's contention that it has a right to influence events in neighbouring post-Soviet states.
Moscow is vehemently against both Georgia and Ukraine joining Nato, and says the organisation is a hostile and expansionist bloc bent on destabilising the region.
Nato has cooled on the idea of giving membership to Georgia and Ukraine after last year's conflict.
But it believes both countries, as sovereign states, have a right to join Nato and other western institutions and transatlantic alliances if they choose to.
Today's exercises involve more than 1,000 soldiers from a dozen Nato member states and partner nations.
Several countries, including neighbouring Armenia, have recently pulled out of the exercises, apparently fearing Russian displeasure.
The manoeuvres are being conducted at a former Russian air force base east of Tibilisi, a few kilometres away from the apparent uprising by a tank division, and get under way fully later this month.
Nato insists the exercises in "crisis response" and field training pose no threat to Russia.
"The Nato secretary general [Jaap de Hoop Scheffer] thinks that nobody should misuse the exercise," Carmen Romero, a Nato spokeswoman, was quoted by Reuters as saying.
"This is not a Nato exercise ... it is an exercise of Nato with its partners.
"This exercise has nothing to do with Georgia, it has nothing to do with Russia. Georgia is just hosting the exercise and nobody should interpret the exercise in a different way and use it for other purposes.'