Members of a group opposing a mosque in the NSW Hunter region have branded the local council "traitors" and pledged the fight is "not over" after councillors voted in favour of its development application.

In a tense meeting at Cessnock City Council on Wednesday night, which was watched over by police, councillors voted 6 - 4 in favour of the mosque and funeral home in the rural area of Buchanan, near Kurri Kurri.

Nathan Paterson holds his fist in the air in a rally against Buchanan Mosque in Cessnock in 2015. Credit:Perry Duffin

The mosque's opponents immediately took to social media to decry the decision and some promoted violence against both the planned place of worship and the council chambers.

"Sounds like the council chambers might need a bomb," one man wrote on an anti-mosque Facebook page, while three separate people proposed setting the mosque on fire.