Some Islamist groups in Syria have "dismissed" the jihadist Islamic State of Iraq and Greater Syria's claim that they have established an Islamic caliphate, according to Reuters Tuesday. 
Nine groups, comprised of Syrian opposition fighters as well as religious scholars, released a statement this week rejecting ISIS's claim of establishing an Islamic caliphate in parts of Iraq and Syria. 
The parties to the statement further rejected ISIS's statement that its leader is now the ruler of the Muslim world Sunday.
ISIS has been successful in overtaking territory in both western Iraq as well as Syria, but continues to fight other rival Islamist fighters in Syria, said the Reuters report.
The statement indicated that the ISIS declaration of the caliphate may be "used as a pretext by foreign powers...to tile the balance against [Syrian] rebels" in their fight against Assad and his regime. Such would in effect "improve his image in the West as a legitimate leader," said the Reuters report.
Among the nine parties that issued the statement is the Islamic Front and the Islamist Coalition, the latter which includes opposition fighters who are supported by Saudi Arabia.  Syrian Islamic scholars who are in exile are also party to the statement.
However, ISIS's main rival in Syria, the Al Qaeda linked Nusra Front, has not yet responded or publicly commented to ISIS's caliphate declaration.
On Tuesday, The Syrian Observatory for Human Rights said that ISIS was in control of most of the towns in the Iraqi border province of Deir Al Zor, where Nusra and ISIS fighters previously clashed for months in an attempt to seize control of the strategic Syrian territory. 
"This announcement will only deepen the conflict with the central Al-Qaeda organization over the legitimacy of who represents it now and as a result who represents true Islam," said Jordan-based Hassan Abu Haniyah,  an expert on jihadist Islamic groups to Reuters.
Al Qaeda denounced ISIS earlier this year, saying that its only representation within the Syrian conflict going forward would be the Nusra Front after tensions arose between Al Qaeda frontman Ayman Al Zawahiri and ISIS leadership, namely Abu Bakr Baghdadi.