The Islamic State jihadist group is reportedly urging Muslim youths everywhere to wage a holy war against Russians and Americans over their crusaders' war in the Middle East.

The call was made through an audio message delivered by ISIS spokesman Abu Mohammad al-Adnani and distributed by supporters of the ultra hard-line group, according to Reuters.

"Islamic youths everywhere, ignite jihad against the Russians and the Americans in their crusaders' war against Muslims," al-Adnani urged in his speech.

He also confirmed the death of another ISIS leader, Abu Mutaz Qurashi, who was reportedly blown up in a US airstrike near Mosul on Aug. 18.

The Mirror reported that the SITE monitoring service previously referred to the senior ISIS official killed in Iraq in August as Fadhil Ahmad al-Hayali.

The White House also said Hayali was the second-in-command of the group.

The audio made no specific mention of ISIS leader Abu Bakr al-Baghdadi, whose health and whereabouts remain unclear following an Iraqi airstrike that hit his convoy recently. The ISIS leader was earlier reported to have been carried in a vehicle after the Iraqi airstrike.

Eight senior figures from ISIS who were meeting in an Iraqi town on Sunday were also reported killed in the Iraqi aerial bombing. However, residents of the town and hospital sources said Baghdadi was not among those killed.

The United States and Russia are currently carrying out separate airstrike campaigns in Syria, which they claim are targeting ISIS.

Washington maintains that Moscow's campaign has mainly targeted other insurgent groups including those that have fought both the ISIS and the Assad regime. Russia had denied the US claims.

The United States is also carrying out airstrikes in Iraq, where Russia has also now become involved. A senior Iraqi parliamentarian said on Tuesday Russian officials are now part of a new Iraq-based intelligence centre with staff from Iran and Syria, Reuters said.