Abu Bakr al-Baghdadi in Mosul
Abu Bakr al-Baghdadi in MosulReuters

The leadership of the Islamic State (IS, formerly ISIS) terrorist group in Syria and Iraq took a sharp blow on Thursday, as roughly 20 senior figures, including a top aide to IS leader Abu Bakr al-Baghdadi, were killed in airstrikes according to the Iraqi defense ministry.

In airstrikes on the northern Iraqi city of Mosul, where IS began its blitz conquest of Iraq in June, Baghdadi's top aide was killed along with a senior IS military commander, Abu Alaa al-Iraqi, according to Iraqi sources cited by BBC.

It remains unclear if the airstrike was conducted by local US-trained Iraqi forces, or by the US, which has been engaged in a series of targeted airstrikes on IS terrorists in Iraq since last month.

IS took a blow in eastern Syria as well, where 18 foreign jihadist senior leaders of the group, including an American jihadist, were killed by an airstrike in the IS-held city of Raqqa according to the Syrian Observatory for Human Rights.

The top IS leaders were in the municipal building of Gharbiya, which has been used as a headquarters for the extremist group, when the strike occurred.

In yet another airstrike in the eastern Syrian city of Abu Kamal near the Iraqi border on Thursday, an as yet unknown number of IS terrorists were killed according to the human rights group. 

During the two airstrikes and the ensuing disorder, a total of 13 IS-held captives were able to escape according to the group.

However, IS was not deterred in its campaign of terror, abducting 40 men from the northern Iraqi Sunni town of Hawija in Kirkuk province on Thursday. Residents of the town said they were uncertain why the men were captured, since IS had captured the town without resistance last month.

The recent airstrikes in Iraq, if conducted by the US, illustrate the increasing seriousness with which America is considering IS after two US journalists, Steven Sotloff and James Foley, were brutally beheaded in executions filmed and broadcast to the world.

After the second journalist was murdered, US Vice President Joe Biden on Wednesday warned IS, saying "they should know we will follow them to the gates of hell until they are brought to justice. Because hell is where they will reside. Hell is where they will reside."