(CNN) -- The head of an al Qaeda-inspired militia fighting in Syria is giving a radical splinter group five days to end infighting and accept arbitration from Sunni clerics or face expulsion from the region, according to an audio message posted online Tuesday.
Abu Mohammed al-Jolani, the chief of al-Nusra Front, called on the Islamic State of Iraq and Syria (ISIS) to stop turning its guns on its allies and return to the fold of al Qaeda's central command.
"I swear by God, if you again refuse God's judgment, and do not stop your plague and pushing your ignorant ideology on the Muslim nation then you will be expelled, even from Iraq," al-Jolani said in the more than eight-minute message produced by al-Nusra Front's media wing al-Manara al-Baydha.
Earlier this month, even top al Qaeda leader Ayman al-Zawahiri weighed in on the situation, and the group's central leadership posted a notice online saying ISIS "is not a branch of the al Qaeda group."
The al-Nusra Front and ISIS are both fighting in Syria. Al-Nusra and other Islamist insurgents argue that the toppling of President Bashar al-Assad's government is the top priority, but ISIS wants the formation of a radical Islamist state to be the main goal.
Apparently, ISIS also has been fighting against al-Nusra members and against civilians who support the opposition.
A conflict in Islamic jurisprudence appears at the core of the long-standing dispute between the Iraqi-born extremist group and its former comrades in al Qaeda.
"Know that we have patiently waited for a whole year while you committed violations, made false accusations, and misconstrued the truth to justify your greater corruption. We relinquished many of our rights," al-Jolani said in the audio message. "You know that until now we have not turned away from the frontlines or fighting the regime as you have done."
The order comes just two days after a suicide bombing allegedly carried out by ISIS killed a mediator representing al-Zawahiri in northern Syria.
Abu Khaled al-Souri's assassination dashed hopes for a political resolution to months of open warfare between ISIS and rebel factions that has claimed the lives of at least 2,000 people, according to the Syrian Observatory for Human Rights, and culminated in the expulsion of the renegade group from al Qaeda's general command earlier this month.
"Al-Zawahiri is clearly fed up with ISIS's open rejection of his overall leadership of the al Qaeda network. Moreover, he is likely quite concerned about how ISIS is alienating ordinary Syrians by a brutal campaign that has involved the public beheading of opponents and the imposition of Taliban-style rule on the population, including the banning of smoking, music and unveiled women in public," Peter Bergen, a national security analyst for CNN, wrote earlier this month.
The bad blood between the two groups started last April when ISIS Chief Abu Bakr al Baghdadi announced his group's expansion into Syria and claimed to absorb al-Nusra Front into his ranks. Tensions rose after al Baghdadi openly refused to heed al-Zawahiri's directive to disband and leave Syria.
Analysts say the factional fighting strengthens the government's hand in the country's nearly three-year civil war by distracting insurgents from engaging in combat with Syrian troops and diverting resources and manpower to the war within a war.