The activists are calling for the state government to review how mines were approved and claim the Maules Creek will endanger fauna in the nearby Leard state forest.
Police were called in to remove up to 170 protestors who blocked access to the mine.
The Leard Forest Alliance is calling for Maules Creek to be shut down and for a parliamentary inquiry to investigate how it received approval, according to AAP.
“These have been flawed, slimy dealings,” the group's spokeswoman Helen War said.
“The whole development process needs to be reassessed.”
Police have confirmed that at least four protesters were arrested and charged.
Whitehaven Coal managing director Paul Flynn reportedly disputed those claims and denied the company's operations had been significantly disrupted.
“(The cost) won't be material for us,” he told ABC Radio.
“There will only be a marginal impact on us for the day.”
Acting NSW resources and energy minister Kevin Humphries said: “The community understands the importance of these projects and the enormous economic benefit they will provide to the region and to the state's economy”
