More than 100,000 civilians have fled the eastern Syrian province of Deir Ezzor because of fierce clashes between rival jihadist groups, the Syrian Observatory for Human Rights said Saturday.

The British-based monitoring group also said the clashes between Al-Qaeda affiliate Al-Nusra Front and the rival Islamic State of Iraq and the Levant (ISIL) had killed 230 militants in the last 10 days.

Of those, 146 were members of Al-Nusra and other Islamist brigades, including some who were executed by ISIL.

The clashes between the two groups in the oil-rich province began at the end of April and come after a wider backlash against ISIL that started in January.

ISIL, which grew from Al-Qaeda's Iraq branch, has been the target of a joint campaign by moderate and Islamist rebels as well as Al-Nusra since early January.

The campaign has pushed it out of much of Aleppo and Idlib provinces, though it has strengthened its presence in the provincial capital of Raqa province.

ISIL was initially welcomed by some of the Syrian opposition, but its abuses of civilians and rebel forces sparked the backlash that begin this year.

In February, ISIL withdrew from most of Deir Ezzor under pressure, but in recent weeks it has advanced once again, the Observatory said, regaining territory in the west of the province.