Russia said Saturday that a Ukrainian diplomat allegedly caught "red-handed" trying to obtain sensitive information must leave the country.
In recent years Russia has detained a number of Ukrainian nationals on suspicion of spying but the detention of a diplomat is rare and seen as a sign of sharply rising tensions."A Ukrainian diplomat, a consul of Ukraine's Consulate General in Saint Petersburg, Alexander Sosonyuk, has been detained by Russia's FSB," the security service said in a statement, using the Russian language spelling of his name.
He was detained on Friday, the security service said. Kiev said the diplomat had spent several hours in detention.
The Russian foreign ministry said later Saturday that it had summoned Ukraine's charge d'affaires Vasyl Pokotylo and told him that the Ukranian diplomat had 72 hours to leave the country "beginning April 19.
"The Russian side pointed to the inadmissibility of such kind of activity," the foreign ministry said in a statement.
Russia's domestic intelligence agency said Sosonyuk had been caught "red-handed" during a meeting with a Russian national as he sought to receive "classified" information.
"Such activity is not compatible with his diplomatic status and is of clearly hostile nature towards the Russian Federation," the FSB said."In conformity with international law, measures will be taken against the foreign diplomat."
In Kiev, foreign ministry spokesman Oleg Nikolenko chalked up the incident to raging tensions between the two countries.
"This is yet another provocation amid Russia's destabilising activities," he told AFP in a statement.
He said Kiev was looking into the incident and would respond "in the near future."
In recent weeks, tensions have escalated between Russia and Ukraine, with Kiev accusing Moscow of massing troops on its border and seeking to destroy "Ukrainian statehood".
Kiev has been battling Russian-backed separatists in eastern Ukraine since 2014 and clashes intensified early this year, shredding a ceasefire agreed last July.
Concern has been mounting that the conflict could spiral back into wider fighting, and Ukrainian President Volodymyr Zelensky has asked the West for help.