A Japanese whaling ship has stopped just outside Australian waters, according to seafaring activists who said they were being chased by the vessel.

The Yushin Maru No 3, one of three Japanese harpoon ships, had been tailing the Sea Shepherd's Bob Barker vessel, members of the anti-whaling group said.

Sea Shepherd said the Bob Barker crossed into Australia's exclusive economic zone 200 miles (320km) from Macquarie Island at 2.50pm on Friday but the Japanese ship stopped about a kilometre outside the zone.

The Sea Shepherd Australia chairman, Bob Brown, said Greg Hunt, the environment minister, had been in touch with Japanese authorities over the impending incursion into the Australian whale sanctuary. Comment was being sought from Hunt by the Australian Associated Press.

"Once again Sea Shepherd has seen the Japanese whaling fleet's tactics thwarted," Brown said in a statement.

"But we are mindful that the fleet is publicly committed to killing another 931 Minke whales as well as 50 fin whales and 50 humpbacks."

Australian whale sanctuary managing director Jeff Hansen said he called Hunt to pass on Sea Shepherd's sincere thanks and appreciation for his efforts.

Sea Shepherd has three ships and about 100 crew members from 21 countries in Antarctic waters to confront Japanese hunting in the Southern Ocean whale sanctuary, where commercial whaling is banned.

Earlier this week Sea Shepherd said its ships drove the Japanese fleet's factory ship, Nisshin Maru, out of the Antarctic treaty zone following a 580km chase.