As fighting continues in Syria, 43 Islamist groups have united to form a joint “Army of Islam.” The groups have agreed to act under the joint leadership of Sheikh Mohammed Zahran.

The Army of Islam’s creation was officially announced in a ceremony Sunday.

The Al-Qaeda affiliated group Al-Nusra, along with ideologically similar groups such as Ahrar el-Sham, did not join the Army of Islam, despite sharing its goal of toppling President Bashar Assad and instituting Sharia (Islamic law) in Syria.

At the same time, the Free Syrian Army is working to reunite its leadership after several commanders disassociated themselves last week from its leadership.

Thirteen rebel brigades announced that they reject the Syrian National Coalition and the Free Syrian Army under the leadership of General Salim Idriss. The groups’ commanders called to unite under an Islamist umbrella group.

The tension between various rebel factions has even led to out-and-out combat. Forces from Al-Nusra recently clashed with Kurdish militias over control of local gas resources and over the institution of Sharia law in Kurdish areas.

Rival Al Qaeda factions have also clashed in recent weeks.

Despite the infighting among Syrian rebels, the various rebel armies continue to hold control over much of Syria, particularly in the Kurdish regions to the north and in villages around the cities of Aleppo, Hama, Homs and Damascus.