"According to the security services, the attacks were planned between March 14 and March 16 in seven (Russian) regions," the NTV channel reported.
It said the group contained three activists from Pravy Sektor, a radical nationalist group in Ukraine, and claimed all 25 were following "instructions" from the Ukrainian security agency, the SBU.
"Their assignments included photographing the location and movement of Russia's military near the border as well as making contacts with Russian radical groups," the report said, adding that those detained were now being questioned.
Earlier today Ukraine's SBU security service said it had detained two Russians in the western Lviv region who had planned to take Ukrainian politicians hostage, including a presidential candidate.
NTV is owned by a bank affiliated to state-owned gas giant Gazprom. It is known for showing smear documentaries that target critics of the Kremlin.