"On 16 April 2021, the Federal Security Service of the Russian Federation caught in the act a Ukrainian diplomat, the consul of the Ukrainian consulate general in the city of St. Petersburg, Oleksandr Sosoniuk, during [his] meeting with a Russian citizen [and] receiving classified information from law enforcement agencies and FSB databases", an official statement read.
"The foreign diplomat will be handled in accordance with the norms of international law", the FSB added.
The FSB noted that the activities of the Ukrainian official were hostile toward Russia and were incompatible with his diplomatic status.
Kiev said it assesses the detention as a hostile action on the part of Russia and is preparing response measures toward Russian diplomats, Deputy Foreign Minister Yevhen Enin said.
"In line with the existing practice and based on the reciprocity principle, the Ukrainian side is preparing a response with regard to Russian diplomats," Enin told the UNN news agency, calling the incident involving the consul "a provocation".