State news agency SANA said the breach came "after the forces advancing from the cemetery southwest of the city linked up with the forces holding the airbase".
The troops had launched a new push today towards the besieged military airport, as part of its multi-pronged offensive to retake the whole eastern city from the jihadists.
Since 2014, IS has held swathes of Deir Ezzor province, which borders Iraq, and about 60 per cent of the provincial capital.
The Syrian Observatory for Human Rights also confirmed troops had breached the siege.
"By breaking the siege on the military airport regime forces have been able to link up all the neighbourhoods they hold in western parts of Deir Ezzor city," the Britain-based monitor said.
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