KYIV (Reuters) -- Ukraine has expelled four Russians for spying and detained another on espionage charges, the head of Ukraine's main intelligence service said.
Spy chief Valentyn Nalyvaychenko said the Russians had been caught in southern Ukraine trying to obtain military secrets.
"Ukraine's security services intercepted a Russian intelligence operation on January 27 in the region of Odessa," 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 a spokeswoman for the security service.
The spy scandal has broken between rounds of a tense election for president in Ukraine in which relations with the former Soviet master, Russia, is an issue.
It came hot on the heels of the arrival of Russia's new ambassador to Kyiv, Mikhail Zurabov, ending a five-month diplomatic rift.
Relations with Moscow had deteriorated under President Viktor Yushchenko but he failed to gain reelection in a first round of voting, prompting Moscow to finalize Zurabov's appointment which had been delayed.
Nalyvaychenko said the spy group -- which included officers from Russia's Federal Security Service (FSB) and a Russian soldier stationed in Moldova's breakaway region Transdniestria -- had kidnapped a Ukrainian in an attempt to gain secrets.
He said four of the Russians had been expelled from Ukraine while an FSB colonel had been arrested on espionage charges.
Digital recorders, a video camera disguised as a fountain pen, flash cards, notebooks, instructions and $2,000 intended to bribe the Ukrainian were found, the security chief said.
A Moscow-based spokesman for the FSB declined to comment.