Fierce clashes gripped the eastern Syrian city of Deir Ezzor on Wednesday (January 18th) as the "Islamic State of Iraq and the Levant" (ISIL) set tires ablaze to create a smokescreen from regime warplanes, AFP reported.

Local activist group Deir Ezzor 24 told AFP on Wednesday that ISIL had executed 10 Syrian regime fighters captured during the ISIL onslaught, launched Saturday to capture the regime-held third of Deir Ezzor city, as well as the adjacent military airport.

More than 150 people are reported to have been killed in the fighting.

Syrian and allied warplanes have carried out intense bombing raids in a bid to halt the group's advance, according to a military source and the Syrian Observatory for Human Rights.

ISIL on Tuesday tried to generate a smokescreen to shield its positions from fresh airstrikes.

"ISIL set tires and barrels of crude oil on fire in Deir Ezzor" to deter the warplanes, the Syrian Observatory for Human Rights said.

Since Saturday, 46 regime fighters and 75 ISIL militants have been killed, along with more than 30 civilians, the Observatory said.

ISIL executed 10 regime fighters on Tuesday night "by driving over them with tanks", said Omar Abu Leila of Deir Ezzor 24, which publishes news on the eastern city.

He said the gruesome killings took place inside ISIL-controlled neighbourhoods of the city.