A top security official in Ukraine who was arrested for alleged collaboration with Russia's Federal Security Service (FSB) is suspected in plotting the assassination of Ukrainian Interior Minister Arsen Avakov.

Avakov's deputy, Anton Herashchenko, said in a televised interview late on April 16 that Major General Valeriy Shaytanov of the Security Service of Ukraine (SBU) is suspected in planning to murder Avakov and Adam Osmayev, the leader of Chechen volunteers who fought alongside Ukrainian soldiers against Russia-backed separatists in Ukraine’s east.

Earlier in the day, the SBU said it detained an unidentified former officer also suspected of collaborating with the FSB along with Shaytanov.

Shaytanov was detained on April 14 on suspicion of high treason and terrorism.

A day later, the FSB announced that it detained a Russian servicewoman and a Ukrainian national in the annexed Crimea region for alleged espionage for Ukraine.

Ukrainian-Russian relations have been strained since 2014, when Russia seized Crimea after sending in troops and staging a referendum deemed illegitimate by at least 100 countries.

In April that year, Russia threw its support behind armed separatists in Ukraine’s eastern regions of Donetsk and Luhansk, where some 13,200 people have been killed in the ongoing conflict.

Based on reporting by Ukrayina 24, Ukrayinska Pravda, and UNIAN