The Britain-based Syrian Observatory for Human Rights said most of those killed appeared to be civilians, adding that the toll could rise further because of the number of seriously wounded.
Syrian state television gave a toll of at least 25 dead, citing Homs provincial governor Talal Barazi.
It broadcast footage from the scene of the attack in the Al-Zahraa neighbourhood, showing the air thick with dust and smoke rising from blazes started by the blasts.
Firefighters ran through debris strewn by the explosions as security forces and civilians tried to prise open the wreckage of one vehicle to retrieve a person inside.
Nearby, a charred body was carried away on a stretcher by emergency services workers.
The bombings appeared to have caused extensive damage, ripping the fronts off shops surrounding the site and mangling cars and minibuses.
The attacks were some of the deadliest to hit the city, which has been regularly targeted in blasts, including a devastating attack at a school in October 2014 that killed 48 children and four adults.
Al-Zahraa neighbourhood in particular has been the target of multiple attacks, including last month, when at least 22 people were killed in a double suicide bombing claimed by the Islamic State group.
Once dubbed the "capital of the revolution," Homs city is now largely controlled by the government.