BEIRUT (Reuters) - The Syrian army said on Wednesday it had killed Islamic State’s military commander in Syria during operations in the north of the country, where the Russian-backed government forces are seizing more territory back from the jihadist group.

If confirmed, this would represent a major blow against Islamic State (IS) ahead of an attack which the U.S.-backed Syrian Democratic Forces (SDF) - an alliance of Kurdish and Arab fighters - are expected to launch against the jihadists in their stronghold of Raqqa city.

A Syrian military source told Reuters the IS commander, Abu Musab al-Masri, had been the group’s “minister of war” for Syria. Syrian state media had earlier cited a military source as saying he was the organization’s “minister of war”, suggesting he was the overall IS military commander.

He was named among 13 senior Islamic State figures killed in Syrian army operations east of Aleppo, including men identified as Saudi and Iraqi nationals, according to the military source cited by state media.

Al-Masri was killed in the operations that got underway on May 10. The military source did not say where he was killed.

Baghdad-based IS expert Hisham al-Hashimi said the death of Masri, if confirmed, would be a “significant blow to the group ahead of the battle of Raqqa”. He said al-Masri was the fourth most senior figure in the organization.

A previous IS minister of war, Abu Omar al-Shishani, was killed last year. The Pentagon said Shishani was likely to have been killed in a U.S. air strike in Syria. The militant group confirmed his death in July but said he had died fighting in the Iraqi city of Shirqat south of Mosul.

Islamic State faces separate campaigns in northern Syria by the Russian-backed Syrian army, the U.S.-backed SDF, and Turkey-backed rebels fighting under the Free Syrian Army banner.

The six-year-long Syrian war has allowed IS to seize swathes of Syria and to carve out a cross-border “caliphate” in both Syria and neighboring Iraq.

The SDF, which includes the Kurdish YPG militia, has been waging a multi-phased operation to encircle Raqqa with the aim of capturing it from Islamic State.