Russia's FSB security service briefly detained a Ukrainian diplomat in St Petersburg, Ukraine's foreign ministry said on Saturday, in the latest flare-up of tensions between the neighbouring countries.
Interfax news agency earlier reported the FSB as saying Oleksandr Sosoniuk was taken into custody when he tried to obtain classified information from Russian law enforcement databases during a meeting with a Russian citizen.
"This activity is incompatible with the status of a diplomatic employee and is hostile to the Russian Federation. The foreign diplomat will be dealt with in accordance with international law," the FSB was quoted as saying.
Ukraine's foreign ministry said Sosoniuk was held for several hours, but was now back at the country's consulate in St Petersburg.
Tensions between Moscow and Kyiv have been rising amid a build-up of Russian troops along the border and clashes in eastern Ukraine between the army and pro-Moscow separatists.
Ukrainian President Volodymyr Zelenskiy on Friday pressed for peace negotiations.
"The Ukrainian side will soon decide how to respond to this provocation, taking into account current practice," Ukraine's foreign ministry said of Sosoniuk's detention.