KIEV - Ukrainian and Russian intelligence services traded accusations on Tuesday after Ukraine said it had expelled four Russians for spying and detained another on espionage charges. The row emerged between rounds of a tense election for president in Ukraine in which relations with the former Soviet master, Russia, is an issue. It also followed closely the arrival of Russia’s new ambassador to Kiev, Mikhail Zurabov, ending a five-month diplomatic rift.

Ukrainian spy chief Valentyn Nalyvaychenko said the Russians, who included members of the Russian FSB state security service, had been caught “red-handed” in southern Ukraine trying to obtain military secrets from a Ukrainian citizen. “Ukraine’s security services (SBU) intercepted a Russian intelligence operation on Jan. 27 in the region of Odessa,” SBU chief Nalyvaychenko was quoted as saying by Interfax Ukraine. “We caught all five operatives red-handed who, with blackmail and threats, tried illegally to obtain Ukrainian state secrets from a Ukrainian citizen,” he said in comments confirmed by an SBU spokeswoman. In Moscow, a spokesman for the FSB confirmed that one of its employees had been detained in Ukraine. But it offered a different explanation for contacts with the Ukrainian, saying he had been held, but later released, at a Russian military post in the Moldovan breakaway region of Transdniestria.