SYDNEY (Reuters): A climate change protest off Australia's east coast disrupted operations at the country's biggest coal export port on Saturday, the port operator said.

Climate activist group Rising Tide, which claimed responsibility for the action, said around 1,500 people were at the protest, 300 of them in the shipping channel near the Port of Newcastle, as part of a 30-hour blockade set to run until 4 p.m. (0900 GMT) on Sunday.

Climate change is a divisive issue in Australia, the world's biggest exporter of thermal coal behind Indonesia, and the top exporter of coking coal, used to make steel.

The Port of Newcastle, some 170 km (105 miles) from New South Wales state capital Sydney, is the largest bulk shipping port on the east coast and Australia's largest terminal for coal exports, according to the state government.

"At present, due to the number of people currently in the shipping channel, all shipping movements have ceased due to safety concerns, irrespective of the cargo they are carrying or intend to load," a Port of Newcastle spokesperson said in a statement.

Rising Tide spokesperson Zack Schofield said no coal shipments had entered or exited the port since 10 a.m. on Saturday.

"So far it's holding true," he said of the blockade by a flotilla of kayaks. In April, 50 of the group's activists were charged by police with an unlawful protest near the same port.

The group wants to block 500,000 tonnes of coal from leaving the port during the blockade, it said in a statement.

State police said no arrests had been made in relation to Saturday's protest.

Australia's centre-left Labor government does not support a ban on all new fossil fuel projects but sees "safeguard mechanism" reforms as key to cutting emissions by 43% by 2030 in a country that ranks as a leading global carbon emitter per capita.

(Reporting by Sam McKeith in Sydney; Editing by Jacqueline Wong and William Mallard) - Reuters