A senior adviser to Ukraine’s defense minister told CNN that Russia’s notorious private military group Wagner was involved in an alleged assassination plot against Ukrainian President Volodymyr Zelensky and Prime Minister Denys Shmyhal.

Lubkivskyi said the plot was confirmed by Ukrainian intelligence and special forces tasked with protecting Zelensky.

“All these documents and the necessary evidence will be presented to the International Court,” he said, adding that he could not reveal more for operational reasons.

CNN was unable to independently confirm the claims.

The Wagner group first became known during Russia’s 2014 invasion of eastern Ukraine. Since then, independent research and CNN surveys found that the private military contractor operated in Syria and several countries in Africa. They have been accused by US officials and human rights watchdogs of persistent human rights abuses.

The group is believed to be linked to – and funded by – Yevgeny Prigozhin, an oligarch so close to the Kremlin that he is known as Putin’s “leader”.

The Kremlin has repeatedly denied any connection to the group. Prigozhin denies any involvement in Wagner.

On Thursday, the UK became the latest country to sanction Wagner.

Lubkivskyi says Ukrainian intelligence services tracked the group inside and outside Ukraine, and several Wagner operatives were killed inside the country, identified by their unique identification tags.

Zelensky has repeatedly pledged to stay in Ukraine to organize the defense of the country during the war, now in its second month.