The armed groups targeted the town of Ein Issa which puts them within 30 miles of the IS stronghold Raqqa, widely seen as the capital of the 'Caliphate'.
Ein Issa was taken hours after Kurdish troops took a nearby Brigade military base forcing even more Islamic State fighters to flee.
IS has been targeting Christians and minorities as it attempts to take over Iraq and Syria.
In Syria a number of Christian men have joined together to form militias to fight against the Muslim extremists.
The town is the last major residential area north of Raqqa to be re-captured, according to the Britain-based Syrian Observatory for Human Rights.
The Christian gunmen and Kurdish fighters are now calling for support and reinforcements to stop the town falling back into IS hands.