The attack left body parts strewn around the area, said Moetez al-Agouri, a police officer at the post, and the death toll was likely to rise as the authorities identified them.
"Seven bodies among the victims have been identified but some other bodies were torn to pieces by the explosion," said Agouri, who was working at the checkpoint at the time but escaped injury.
Eight people including civilians were wounded in the attack on the checkpoint 50 kilometres (30 miles) east of Benghazi and were taken to hospital in the nearby town of Tokra, Agouri said.
Benghazi, the cradle of the 2011 uprising that toppled longtime dictator Moamer Kadhafi, has seen a series of attacks in recent months that have killed more than 300 people.