ST PETERSBURG • Russia said it would expel a Ukrainian diplomat, prompting an immediate pledge of retaliation from Kiev, further escalating tension over Moscow's troop build-up on Ukraine's eastern flank.
The detention of a Ukrainian consul in St Petersburg comes at a time of global concern of a repeat of Moscow's 2014 aggression, when Russia annexed the peninsula of Crimea and backed separatists in Ukraine's east.
Moscow claimed on Saturday that the diplomat had been caught "red-handed" trying to obtain sensitive information.
In response, the Ukrainian Foreign Ministry protested against the "illegal" detention and said Kiev would expel a senior Russian diplomat.
Kiev has been battling Russian-backed separatists in eastern Ukraine since 2014 and clashes intensified early this year, effectively shredding a ceasefire agreed last July.
Around 30 Ukrainian troops have been killed since the beginning of the year, compared with 50 last year. Most were victims of sniper fire.
Russia has detained a number of Ukrainian nationals on suspicion of spying in recent years, but the arrest of a diplomat is rare.
Russia's Foreign Ministry said on Saturday it had summoned Ukraine's charge d'affaires Vasyl Pokotylo and told him that the diplomat had 72 hours to leave Russia, "beginning April 19".
The country's domestic intelligence agency noted that Mr Alexander Sosonyuk had been caught "red-handed" during a meeting with a Russian national as he sought to receive "classified" information.
In Kiev, the Ukrainian Foreign Ministry said it protested against the detention and rejected the accusations.
Spokesman Oleg Nikolenko said Russia had "crudely" violated diplomatic conventions and sought to intensify tensions.
"In response to the above-mentioned provocation, a senior diplomat of the Russian embassy in Kiev must leave Ukrainian territory within 72 hours beginning April 19," he added.
Faced with the largest deployment of Russian troops on Ukraine's borders since 2014, President Volodymyr Zelensky has requested more help from the West, and Western leaders have urged Russian President Vladimir Putin to stop the intimidation.
Tensions between Russia and Ukraine come against the background of a new war of words between Moscow and Washington as new United States President Joe Biden seeks a tougher line against Mr Putin.
The US last Thursday announced sanctions and the expulsion of 10 Russian diplomats in retaliation for what the White House said was the Kremlin's US election interference, a massive cyber attack and other hostile activity.
Moscow said last Friday it would expel US diplomats and sanction officials while recommending the American envoy to leave Russia "for consultations".
Ukraine is not the only diplomatic flashpoint between Moscow and the West.
On Saturday, the Czech authorities announced they would be expelling 18 Russian diplomats identified by local intelligence as secret agents of the Russian foreign intelligence services.
They are suspected of involvement in a 2014 explosion at an ammunition depot that killed two Czechs.
Last Thursday, Poland said it had expelled three Russian diplomats for "carrying out activities to the detriment" of the country.
Earlier this month, Italy expelled two Russian envoys after it said an Italian navy captain had been caught handing over classified documents to a Russian agent.
Meanwhile, French President Emmanuel Macron said the international community has to "define clear red lines with Russia" in an interview extract released on Saturday, adding that countries must be ready to impose sanctions in case of "unacceptable behaviour".
He added during the interview with US network CBS that the world needed to make it clear to Moscow that while it preferred "open and frank dialogue", it will not shy away from imposing sanctions after any "unacceptable behaviour".
"I think that sanctions are not sufficient... in themselves, but sanctions are part of the package.
"I do prefer constructive dialogue, but to have a constructive and efficient dialogue, you need credibility," Mr Macron said.