Ukraine’s Security Service (SBU) says it has breached an espionage communication channel between a high-ranking Ukrainian naval officer and staff from Russia's main spy agency, the FSB, in the Russian-occupied Crimean Peninsula.

Procedures have begun to strip the officer of access to classified data and strip him of his rank, the SBU said in a statement on March 31, according to RFE/RL.

It did not give the officer's name, former rank, or current status.

According to the statement, the officer maintained his loyalty to Kyiv while he was in service in Crimea when Russia took over the peninsula in 2014. It said the officer refused to assist Russian security forces in occupying a naval academy in the port city of Sevastopol.

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However, upon being redeployed to mainland Ukraine after the Russian invasion, the officer continued to "maintain constant contacts with FSB operatives in acting service," the SBU said.

Among them were "former SBU servicemen Andrey Gaponenko, Petro Zima, Dmitry Pylypchenko, who flipped to the enemy's side during the annexation of the Autonomous Republic of Crimea in 2014."

After moving to mainland Ukraine, the officer visited his native Crimea and allegedly had personal meetings with the ex-SBU operatives, according to the statement.

It said the navy officer had "access to classified information that is of a particularly important nature related to defense."

The SBU published a video on social media allegedly showing the man making confessions.