The ongoing rivalry between ISIS and Al Qaeda has reached new heights this week, with ISIS distributing "Wanted Dead" posters for several key Al Qaeda commanders - including the group's leader, Ayman al-Zawahiri

The posters began circulating earlier in August and were apparently the work of ISIS's official branch in Libya. ISIS has been fighting various other militias for control in the North African country, which has slipped into a state of lawlessness after the ouster of dictator Muammar Gaddafi in 2011.

In the initial stages of the campaign, dozens of posters were released offering bounties for the heads of the Mujahideen Shura Council (MSC) - an Al Qaeda-linked Islamist coalition that is currently battling ISIS for control of the eastern Libyan city of Derna.

The MSC has proven a tough adversary and has thwarted ISIS's attempts to take the city thus far. However, several of its leaders have indeed been successfully targeted since the campaign started. According to the Long War Journal, "Each time one is killed, the Islamic State’s supporters release a new version of the graphic, changing the format and color to signify his death."

Other Libyan militia heads have also been targeted.

But the campaign soon expanded beyond Libya, to include the leader of Algeria's Al Qaeda branch (Al Murabitoun).

And on Sunday, ISIS released the most provocative poster yet, placing a bounty on the head of Al Qaeda's elusive leader, Ayman al-Zawahiri, who took over after the 2011 assassination of Osama Bin Laden by US Special Forces.

ISIS - or "Islamic State," as it refers to itself - officially broke off from Al Qaeda in February 2014, after a protracted power-struggle between Zawahiri and ISIS's leader, Abu Bakr al-Baghdadi.

Soon after, Baghdadi declared a "Caliphate" in areas of Syria and Iraq under ISIS control, and named himself "Caliph," or supreme Muslim leader. The move further infuriated Al Qaeda, which did not recognize Baghdadi as Caliph.

Since then, the two groups have been locked in a bloody war, particularly in Syria, with each referring to the other as "apostates."

Still, an open call to kill Al Qaeda's leader - who is currently believed to be hiding in the mountainous Afghanistan-Pakistan border region - marks a new benchmark in the animosity between the two terrorist groups.