The focus of IS counter-attacks has been aimed at retaking Sirte's port and western sectors of the city, the hometown of late dictator Moamer Kadhafi, military sources said.
Jihadist groups took root in Libya in late 2014, taking advantage of the chaos and power struggles that followed the NATO-backed uprising that toppled and killed Kadhafi in 2011.
"A suicide attack using a booby-trapped car targeted the Abu Grein checkpoint," the forces of the Government of National Accord said in a statement sent to AFP.
Thirty-two people were killed and 50 wounded in a car-bomb attack in Abu Grein the next day targeting the forces allied with the GNA.
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Ten members of the pro-GNA forces were killed and seven wounded in today's blast at Abu Grein, said sources at the central hospital in Misrata, from where they launched an offensive against the jihadists.
The military command of the anti-IS operation said two other car-bombings inside Sirte itself were foiled today.
"The two cars had targeted positions of our forces on two fronts."
The jihadists have mounted eight suicide car bombings against pro-GNA forces since Sunday, as they intensify efforts to regain lost ground in the Mediterranean city.
The pro-GNA forces backed by air strikes entered the city last week, aiming to drive the extremist group out of its bastion on Europe's doorstep.
But the advance has been stalled since Sunday on the outskirts of Sirte's residential areas where the jihadists are holed up.
Established in Tripoli more than two months ago, the UN-backed unity government has been struggling to exert its control over the North African country, which is awash with weapons.
Unity government head Fayez al-Sarraj said this week that the GNA forces' advances in Sirte should be a model for "a national initiative to fight terrorism".