Russia said Sosoniuk was detained for allegedly trying to obtain confidential information.
Russia’s FSB security agency briefly detained a Ukrainian diplomat in St Petersburg, Ukraine’s Foreign Ministry said on Saturday, during the latest outbreak of tensions between neighboring countries.
The Interfax news agency previously reported citing the FSB that Oleksandr Sosoniuk was arrested when he tried to obtain confidential information from Russia’s law enforcement database during a meeting with a Russian citizen.
“This activity is incompatible with the status of a diplomat and is hostile to the Russian Federation. Foreign diplomats will be dealt with according to international law, ”the FSB was quoted as saying, adding that Sosoniuk was detained on Friday.
Ukraine’s Foreign Ministry said Sosoniuk was held for several hours but has now been returned to the country’s consulate in St Petersburg.
“The Ukrainian side will soon decide how to respond to this provocation, taking into account current practice,” it added.
In recent years, Russia has arrested some Ukrainian citizens on suspicion of espionage, but the incarceration of a diplomat is rare.
Tensions between Moscow and Kyiv are growing amid rising Russian troops along the border and clashes in eastern Ukraine between the army and pro-Moscow separatists.
Kyiv has been fighting Russian-backed separatists in eastern Ukraine since 2014, and clashes have increased since the beginning of the year, breaking a ceasefire agreed on last July.
On Friday, Ukrainian President Volodymyr Zelenskyy urged peace talks.