Beirut, Asharq Al-Awsat—The Islamic State of Iraq and Syria (ISIS) continues to gain ground in eastern Syria, raising fears that the Al-Qaeda-inspired group in Syria will be able to unite with ISIS fighters in control of territory in Iraq’s western Anbar province.

In comments to Asharq Al-Awsat, Syrian Observatory for Human Rights director Rami Abdulrahman said that ISIS has wrested control of the entire rural area expanding from eastern Aleppo to the western parts of the oil-rich district of Deir Ezzor, along the borders with Iraq.

Clashes were reported on Thursday between ISIS and moderate Islamist rebels who were driven further to the south, said Abdulrahman.

Activists said that a large numbers of civilians fled the village of Salhiya north of Deir Ezzor after ISIS warned they intended to storm the oil-rich area.

According to the Observatory, moderate Islamist rebel factions, mainly belonging to the Al-Nusra Front and the Islamic Front coalition, have seized the southern part of the district.

“These developments mean that [moderate] Islamist fighters have made no progress in light of the ISIS advance,” Abdulrahman said, highlighting that “Al-Nusra Front fighters retreated from the western countryside of Deir Ezzor following an attack from 70 well-organized and well-trained Chechen and Afghan fighters belonging to ISIS.”

ISIS fighters are also present across the border in Iraq’s restive Anbar province, where central government forces backed by local tribes are seeking to dislodge them. The militant group has been in control of territory in the western Anbar province, including parts of the cities of Ramadi and Fallujah, since last year.

There are fears that the group is seeking to secure the border region between its two areas of influence in Iraq and Syria, securing a single unified cross-border territory under the group’s command.

ISIS has said, via its leader Abu Bakr Al-Baghdadi, that it aims to establish an Islamic Emirate in the Levant, with international media this week reporting that the group’s advance in Iraq and Syria is threatening Al-Qaeda’s predominance among Islamic extremist groups. The Al-Nusra Front is the official Al-Qaeda-affiliated franchise in Syria and is currently fighting ISIS in the east of the country. Al-Qaeda leader Ayman Al-Zawahiri has called on ISIS and the Al-Nusra Front to put aside their differences and concentrate on fighting the Assad regime.