Russia has accused Ukraine of carrying out a number of high-profile attacks against prominent Russians since Moscow invaded its neighbor nearly four years ago.

Ukraine’s Security Service has claimed responsibility for killing Lt. General Igor Kirillov, head of the military’s nuclear, biological and chemical protection forces, in a bombing in Moscow.

Russia’s top investigative agency on Saturday said the suspect in a car bombing that injured a prominent pro-Kremlin novelist and killed his driver has admitted acting at the behest of Ukraine’s special services.