At least 13 terrorists were killed in a blast in the city of Homs in central Syria on Sunday as they primed a car bomb for an attack.

At least 13 terrorists were killed in a blast in the city of Homs in central Syria on Sunday as they primed a car bomb for an attack.

The opposition UK-based Syrian Observatory for Human Rights said at least 13 gunmen were killed in the besieged Old City of Homs when a car bomb exploded.

"The death toll is likely to rise because there are dozens of people missing and body parts in the area of the blast," the group said.

State news agency SANA also reported the blast, saying a car had exploded while being loaded with explosives.

The blast took place on the outskirts of the besieged Old City of Homs, which is under armed groups' control.