A protest group says around 50 people have been arrested during demonstrations at the Maules Creek mine site near Narrabri in north-western New South Wales.

Mining company Whitehaven Coal operates the site and has been recently clearing land in the Leard State Forest.

Environmental groups are worried that clearing in winter will endanger hibernating animals.

The protest group, the Leard Forest Alliance, says around 100 people attended and up to 50 people were arrested today.

Alliance spokesperson Helen War says those arrested had blocked one of the access roads.

"Some were fined and some were given summons and they were moved offsite by paddy wagon," she said.

Police have confirmed there was an incident at the site, but are unable to confirm the number of people arrested or if charges have been laid.

Ms War says the protesters planted seedlings on a newly-cleared patch of land at the site, as a symbolic act against land clearing.

"I guess it's a gesture of hope, just like the rest of the trees that have been bulldozed, they're probably going to to get re-bulldozed again," she said.

"There were a lot of people here who felt it was a powerful gesture and a gesture that says this is the world that we want to create and we want to live in."

Protesters against Whitehaven Coal's expansion plans for the Maules Creek mine in Sydney on June 4. ( Audience submitted: Kate Ausburn )

In the past few days, another protest group, the Maules Creek Community Council, launched civil action against Whitehaven Coal over its winter clearing.

Earlier this month about 200 farmers and environmentalists protested in Sydney against the project saying they had legal advice suggesting changes to the biodiversity management plan should not have been approved by the State Government.

Senior police have been concerned by recent actions of several anti-coal protesters who have previously chained themselves to mining equipment. Two people were arrested in late May.

Whitehaven says the Maules Creek project involves one of the largest coal deposits in Australia and could continue operating for up to 30 years.

It estimates the construction phase will cost $767 million and says it is one of the most significant investments currently underway in regional New South Wales.

The company says when operating at full capacity the mine is expected to employ about 450 people.