It would be the first time Ukrainian forces managed to hit an S-400 system in mainland Russia.

Ukraine damaged one of Russia’s most treasured air-defense system in a drone attack, according to multiple reports.

Using multiple strike drones, the Security Service of Ukraine (SBU) damaged a Russian S-400 Triumph anti-aircraft system on Wednesday, The Kyiv Post reported on Wednesday, citing an intelligence source.

The SBU source did not elaborate on the extent of damage done, though Reuters reported that the system’s radar was affected.

The attack occurred at night time inside mainland Russia, near the southwestern city of Belgorod, according to Ukrinform and Reuters.