ISIL advances in Deir Ezzor

(15/7) 'Islamic State' expels rivals from Syria city: "Islamic State killed the Deir Ezzor chief of [Jabhat] al-Nusra and raised their flag in the city," according to the Syrian Observatory for Human Rights.

The group calling itself the Islamic State, previously known as the Islamic State of Iraq and Levant [ISIL], has taken control of the rebel-held portion of the eastern Syrian city of Deir Ezzor,  buoyed by advances in neighbouring Iraq  has said.  Rival rebel groups fighting against forces loyal to President Bashar al-Assad either changed sides or fled from the strategic Euphrates valley city.

According to the [SOHR], which relies on a network of activists and medics on the ground, fighters from the Islamic State group were now in control of "95 to 98 percent of Deir Ezzor province". The regime-controls half of Deir Ezzor city, a handful of villages as well as the military airport.

The Observatory said that rivals of the Islamic State group,  including fighters of al-Qaeda's Syria affiliate, Jabhat al-Nusra, lost control after negotiations failed with the Islamic State group whose leadership last month declared a "caliphate" straddling Syria and Iraq. "Fighters from Jabhat al-Nusra and the [Islamist] rebel movement Ahrar al-Sham withdrew from their bases in the city, while others pledged their loyalty to [the] Islamic State," the Observatory said.

The rebel spokesman for Deir Ezzor confirmed the reports, blaming international backers of the anti-Assad opposition for a lack of support. Speaking to the AFP news agency via the Internet, Omar Abu Leyla said: "The withdrawal is a result of the lack of any formal financial backing [for the rebels] either from the [exiled] opposition or from the international community." [..]

[ISIL's] gains in Iraq have tipped the balance in the struggle for power in rebel-held areas of eastern and northern Syria where it has been fighting armed groups allied with al-Nusra since January. The Islamic State group already controls the city of Raqqa upstream from Deir Ezzor where it has enforced its hardline form of Islam,  with public executions,  including crucifixions. Abu Leyla added: "Islamic State has no shortage of weapons,  ammunition or fighters,  and the battle became totally asymmetrical, especially after its advance on Mosul and its capture of heavy weapons." (see also NGO: Jihadists expel rivals from Syria’s Deir Ezzor.)

It seems to me that, largely unnoticed, there is a tragedy unfolding for the Syrian people and the broad alliance of groups that are fighting the regime. 

In an earlier report, Omar Abu Leyla was described as a Free Syrian Army spokesman: "But in four months of fighting (in Deir Ezzor), the rebels who were fighting IS did not receive a single bullet" from countries that back the revolt, he complained. (Islamic State 'seizes key Syria oil field', 3/7)

Only 3 weeks previously, Syria Deeply published, "As ISIS Looks Deeper into Deir Ezzor, Nusra Remains Formidable Opponent" (27/6):

even before its Iraqi surge, ISIS was steadily gaining ground in Deir Ezzor, because that is where it has focused its main combat resources in Syria. ISIS pulled back months ago from the main fronts with the regime in the north, and it has focused on seizing control of Deir Ezzor rather than seeking to gain significant ground elsewhere in the country. In contrast,  al-Nusra and leading rebel factions fight ISIS in Deir while continuing to bear the burden of battles with the regime in Aleppo and throughout the north.

President Obama has asked the US Congress to approve $500m

 to train and equip what he described as "moderate" Syrian opposition forces.  The funds would help Syrians defend against forces aligned with President Bashar al-Assad, the White House said. The aid would also counter Islamist militants such as the Islamic State in Iraq and the Levant (Isis), it added.  [..] it is unclear whether and when Congress would act on his request. (26/6)

Update (2 Aug.)
Jeff Weintraub links to my post, with some comments:

what all this means is that the less extremist, non-jihadist groups in that area had already been forced into an alliance with the Al-Nusra Front, an affiliate of Al Qaeda, in a last-ditch effort to resist ISIS,

I don't think they were forced into an alliance with Jabhat al-Nusra because of the threat from ISIL: they have been fighting alongside JN against the regime for a while; when the US State Department designated JN as a terrorist organization in late 2012 / early 2013, the Syrian Opposition Coalition spoke out against the decision.