The head of the Ukrainian security service, Valentyn Nalyvaichenko, said at a news conference on Wednesday that the accused spy, Lt. Col. Mykhailo Chornobai, had been at the center of an espionage ring in the capital and had passed military secrets directly to an agent of the separatist Donetsk Peoples Republic, including the locations of volunteer regiments that were then used to pinpoint artillery attacks.
Dmytro Tymchuk, a military officer and member of Parliament, said that Colonel Chornobai was among about 300 people working in the military sphere who had been arrested since the start of the conflict.
The arrest further deepened mistrust of the leadership in Kiev that is already pervasive among the poorly equipped rank-and-file soldiers and midlevel commanders fighting on the front line. And it reinforced a view prevalent on the battlefield that the military leadership cannot be trusted to manage any weapons delivered by Western allies because of their ties to the Russian military and security service, the F.S.B.
Mr. Semenchenko, in an interview before he was wounded over the weekend in heavy fighting in Debaltseve, said that on a recent visit to Washington he had urged officials to send aid directly to the front, bypassing the general staff.