Ukrainian Security Service SBU detained a serviceman, accused of leaking the location of Ukrainian troops to Russia in Moscow's offensive in Kursk.
Ukraine's SBU on Tuesday said the serviceman was giving away locations of Ukrainian soldiers to the Russians.
"While at the front, the 'mole' was preparing coordinates for the aggressor's missile and bomb attacks on the locations of Ukrainian troops," the SBU said.
It further stated that the serviceman had been recruited by Russia's GRU military intelligence service via Telegram, where he had posted comments in support of Russia.
In August last year, Ukrainian forces crossed the border into the Kursk region in a rapid offensive, hitting back against Russia following its 2022 invasion of Ukraine.
Since then, Russia has taken back much of the territory that was captured in the Ukrainian advance into Kursk, however, fighting there continues.
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Moreover, the GRU does not usually comment on SBU statements about recruited agents. It made no public comments on Tuesday as well.
Ukraine's military reported 18 clashes on the Kursk front over the previous day.
Ukraine has also been hoping that the Russian city would act as a bargaining chip in future talks and force Russia to divert troops away from its offensive in eastern Ukraine.
However, Ukraine's troops in Kursk have seen their position worsen in recent weeks as Russian forces pushed back.
US President Donald Trump also urged his Russian counterpart Vladimir Putin to spare the lives of thousands of Ukrainian troops, saying that they were in a "very bad and vulnerable position”, without elaborating on what he was referring to.
Putin responded to that and said that he would spare the lives of Ukrainian troops in the Kursk region if they laid down their arms.
(With inputs from agencies)