KIEV, Ukraine — A spying scandal between Ukraine and Russia threatens to heighten tensions between the countries as Ukraine's holds a presidential runoff election Sunday between a Russian-leaning candidate and Prime Minister Yulia Tymoshenko.
Ukraine's security service said Wednesday five Russians were detained last month after being caught trying to obtain confidential military information from a Ukrainian citizen.
"We have broken up an FSB spying operation," Ukrainian security services spokeswoman Marina Ostapenko said.
Russia's Federal Security Service, or FSB, confirmed its agents had been detained, but accused Ukraine of sensationalizing the issue.
"It was surprising the Ukraine Security Service's leadership was so hasty in publicizing this incident, because this kind of situation is usually resolved by cooperation between the special services," said an FSB spokesman, who declined give his name.
Ukraine's security service says the FSB agents tried to use "blackmail and threats" to force a Ukrainian citizen to reveal state secrets.
"We are deeply concerned by the outrageous behavior of these spies and about the safety of our citizens," Ostapenko said.
Ostapenko says four of the officers, who were apprehended in a sting operation late last month, have been expelled and another faces espionage charges.
The officers had digital voice recorders, pen-shaped miniature video cameras, memory cards disguised as key-chains, other electronic equipment and $2,000 in cash when they were arrested, Ostapenko said.
The FSB says the Ukrainian citizen its agents were working with had himself been apprehended in November while allegedly spying on neighboring Moldova's Moscow-backed breakaway Trans-Dniester republic.
The Ukrainian agent was held briefly at a Russian military base and later agreed to assist in intelligence operations in Ukraine, the FSB said.
The election is being bitterly contested between Russian-leaning Viktor Yanukovych and Tymoshenko, a leading figure in the 2004 Orange Revolution.
Russia and Ukraine have clashed repeatedly in recent years over everything from the status of the Russian language to Ukraine's bid to join NATO. The Orange Revolution, which kept Yanukovych out of power, was reviled in the Kremlin, which has since taken firm steps to avoid a similar opposition movement from arising in Russia.
Russian news agency Interfax cited influential pro-Yanukovych deputy Mykola Azarov as saying Wednesday that the spy scandal was aimed at damaging relations between Russia and Ukraine.
Yanukovych beat Tymoshenko 35 percent to 25 percent in the first round of voting of the presidential election Jan. 17. But analysts expect Tymoshenko to close that gap by picking up votes splintered among candidates in the first round.
(This version CORRECTS spelling to Moldova's sted Moldavia's.)