The Ukrainian Security Service (SBU) on Wednesday accused Russian intelligence forces of instigating the current pro-Moscow unrest in eastern Ukraine.

"The conversations between Russian agents, intercepted by the SBU, indicate that permanent officers of the Russian military intelligence are supervising sabotage operations in Ukraine's east," the SBU's press service said in a statement on its website.

Russian officers gave "cynical instructions" to pro-Moscow activists, in particular "orders to shoot to kill at Ukrainian officers," the statement said.

Earlier in the day, unidentified men bearing Russian flags, some in balaclavas and wearing military fatigues, had driven armored vehicles and tanks into the towns of Kramatorsk and Slavyansk after Kiev on Tuesday launched "anti-terror" operations against the alleged separatists.

A new wave of unrest erupted in Ukraine's east over the weekend, as pro-Moscow activists seized several administrative buildings in nearly 10 eastern cities, demanding a referendum on autonomy and closer ties with Russia.

On Monday, Russian Foreign Minister Sergei Lavrov dismissed accusations that Moscow was destabilizing Ukraine, saying that Russia does not interfere in its neighbor's internal affairs.