Ukraine has confirmed it will expel a 'senior' Russian diplomat on Monday in response to the arrest and expulsion of its consul in St Petersburg.
Russia has ordered a Ukrainian diplomat it accused of receiving 'classified information' to leave the country, prompting Ukraine to expel a Russian diplomat in response.
Early on Saturday the Federal Security Service (FSB), Russia's main security agency, said it had taken Alexander Sosonyuk, Ukraine's consul in St. Petersburg, into custody on Friday.
The FSB claimed Sosonyuk had been apprehended "red handed" a meeting with a Russian in which he received “information of a classified nature contained in the databases of law enforcement agencies and the FSB".
The statement added "This activity is incompatible with the status of a diplomatic worker and is clearly hostile towards the Russian Federation."
Later the Russian foreign ministry informed charge d’affaires Vasily Pokotilo that Sosonyuk must leave the country by Thursday. No details about the contents of the classified material have been made public.
The Foreign Ministry of Ukraine has since confirmed that it will be expelling an as-yet unidentified "senior" Russian diplomat on Monday in response to the move.
In response to a request for comment from Euronews, a spokesman said: “Against the backdrop of Russia’s escalation of the security situation and massive anti-Ukrainian propaganda, the Russian side continues provocations against staff members of Ukrainian diplomatic missions in Russia.
"We strongly protest against the April 16 illegal detention of a staff member of the Consulate General of Ukraine in Saint Petersburg, and the order for him to leave the territory of the Russian Federation until April 21. We absolutely reject the accusations made against the consular officer.
"In response to this provocation, a senior diplomat of the Russian Embassy in Kyiv has been ordered to leave the territory of Ukraine within 72 hours, starting April 19.”
The arrest has come amid escalating tensions between the two countries over Russia's huge military buildup along the border with eastern Ukraine.
On Thursday, Russian also announced the closure from next week to October 2021 of part of the Black Sea in the direction of the Kerch Strait, for the purposes of "military exercises".