State news agency SANA confirmed the attack but gave no precise toll.
"Eight people were killed in a car bomb attack on a checkpoint guarding the Firqlos gas plant in Homs province, and 15 others were wounded. Four of the dead were regime troops," said the Syrian Observatory for Human Rights.
The Britain-based group, which relies on a broad network of sources for its reports, said it was not clear if suicide bombers had carried out the attack.
The agency, quoting a military source, said "guards captured the two terrorists who detonated the pick-up truck at the entrance to the plant, while they were trying to flee."
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There was no immediate claim of responsibility for the attack.
The jihadist Islamic State (IS) group has targeted oil and gas facilities in Iraq and Syria as it seeks funds for its fight to seize territory for a self-proclaimed Islamic "caliphate
In November, Syrian troops backed by pro-regime militiamen recaptured the Shaer gas field in central Homs province, a week after it IS fighters had overran parts of the installation.