KIEV, Ukraine — Ukraine’s security service said Saturday it has detained a 15-strong armed gang planning to seize power in an eastern province on the border with Russia.

The Security Service of Ukraine said it seized 300 machine guns, an antitank grenade launcher, a large number of grenades, five handguns and petrol bombs.

It said the group intended to mount a grab for power in the Luhansk province on April 10 by sowing panic among the local population. No names or additional details were provided.

Luhansk and neighboring mainly Russian-speaking eastern provinces have seen active calls for separatism following February’s toppling of President Viktor Yanukovych. Ukraine’s pro-European interim government accuses Russia of fomenting secessionist sentiments.

The Crimean Peninsula was annexed by Russia last month following a contentious referendum.

Earlier in the week, a state-controlled Russian TV station said 25 Ukrainian citizens had been arrested in Russia by the country’s security agency on suspicion of planning sabotage.

NTV television reported Thursday that those arrested included three activists from Right Sector, a Ukrainian nationalist group that played a role in Yanukovych’s ouster. The report didn’t say when the suspects were arrested or give their names but included footage of three suspects in custody.