Australian climate change group Rising Tide stopped operations at all three terminals operated by Port Waratah Coal Services in Newcastle on Sunday.

About 50 people in total were involved in the protest, some entering before dawn and descending down machinery and attaching themselves to loaders.

A spokesperson for Rising Tide said nine protesters attached themselves to infrastructure, calling it an emergency action to highlight climate change.

New South Wales state police confirmed that protesters had entered the facilities and tied themselves to machinery.

A police spokeswoman said negotiations with the protesters were underway.

Port Waratah Coal services said it would be several days before losses resulting form the action could be assessed.

Newcastle is the world's largest coal export port and a major earner of foreign exchange for Australia.

Coal is one of Australia's leading exports, but the industry is opposed by the country's influential climate change lobby.