Russian Lieutenant General Valery Asapov has been killed by Islamic State mortar fire near Deir ez-Zor city in eastern Syria.

The commander of the 5th Combined Arms Army, Asapov (pictured) was said to be in a field headquarters near the city. He is the highest-ranking officer to be killed since the breakup of the Soviet Union in 1991.

Accounts differ on whether there were other casualties. Some outlets on Russian social media said that two colonels were killed as well, but others said only a translator was with Asapov when the headquarters was struck.

The Russian Defense Ministry referred Asapov as the “head of a military advisory group”. It did not mention other fatalities and does not give the date of the incident.

Asapov served in Chechnya and was severely wounded in the leg during the January 1995 assault on the capital Grozny. He later was in the Abkhazia peacekeeping force, fought in the Second Chechen War, and commanded the 18th Machine Gun and Artillery Division on the Kuril Islands.

In March 2016, Ukrainian military intelligence claimed Asapov, now a Major General, arrived in Donetsk in Eastern Ukraine and commanded the 1st Army Corps of separatist forces — an allegation repeated bgy the secretary of Ukraine’s National Security and Defense Council in July. However, as of October 2016, Asapov was serving in Russia’s Eastern Military District as the commander of the 5th Army.