Kisiev said the detention took place at a polling station set up at a Russian school, where many diplomats and police officers were present.
"Well, the Serbian police have detained me outside the Russian embassy. Fun," the political strategist wrote. He later clarified that he had mixed up the location: "I realized afterwards that it wasn't the Russian embassy."
Kisiev said "nothing bad happened" and promised to give details later. He did not give a reason for the detention.
Dmitry Kisiev headed the campaign staff of Boris Nadezhdin, who ran in Russia's 2024 presidential election. Russian authorities refused to register Nadezhdin at the time.
Kisiev was born in Dzhankoi in Crimea and received Russian citizenship after the peninsula's annexation in 2014. In July 2025, he said he had been stripped of his Russian citizenship.
Election campaigns at various levels are being held in Russia on September 18-20, including elections to the State Duma. Most polling stations abroad opened on the morning of September 20.