A Ukrainian official who was present during the first peace talks between Ukraine and Russia was killed during a mission over the weekend. Ukraine confirmed the official was one of three spies who were killed, but did not say how, and media reporting said he was suspected of treason.

The Main Directorate of Intelligence of Ukraine’s Ministry of Defense (GUR) first revealed the death of Ukrainian intelligence operative Denis Kireyev in a Facebook post on March 5. Two other Ukrainian intelligence operatives, Oleksiy Dolya and Valeriy Chibineyev, were also killed over the weekend, the post stated.

“They died defending Ukraine; their deeds have brought us closer to victory!” the post read. “On behalf of the Central Intelligence Agency, we express our sincere condolences to the families of the victims.”