Australia is sending a ship to pick up two activists detained on a Japanese whaling ship as Canberra tries to ease a tense standoff between the two sides.

Foreign Minister Stephen Smith says Thursday an Australian customs ship, the Oceanic Viking, will pick the two men up - an Australian and a Briton - but stressed that it would be a difficult operation.  He urged both sides to show restraint.

Anti-whaling activists are threatening more action against the Japanese whaling boat for holding their two colleagues.  The Japanese whaling fleet is demanding activists stay 10 nautical miles away and stop disrupting their hunt.

Anti-whaling activists have called the whalers' conditions unacceptable and said they will continue to try and stop the whale hunt. 

Japan says the two activists illegally boarded their harpoon ship and attacked crewmen with bottles of acid.  Anti-whaling activists say their colleagues are being mistreated and have called their detention a kidnapping.

Some information for this report was provided by AFP and AP.