Japanese whalers will set out for the Antarctic this week, but will leave their harpoons at home after the United Nations' top court last year ruled their annual hunt was illegal, the government said Tuesday.

The Japanese Fisheries Agency said the Institute of Cetacean Research plans to conduct non-lethal research on whales until March 28.

As the research does not involve catching whales, harpoons have been removed from the vessels, the agency said.

Two boats, which will set sail on Thursday, will carry out "sighting surveys" and take skin samples from the huge marine mammals. A third boat will sail in support.

The International Court of Justice -- the highest court of the United Nations -- ruled in March that Tokyo was abusing a scientific exemption set out in the 1986 moratorium on whaling, and was carrying out a commercial hunt under a veneer of research.

After the ruling, Japan has said it would cancel this winter's Antarctic mission.

But Tokyo has also expressed its intention to resume "research whaling" in 2015-16.

In a new plan submitted to the International Whaling Commission (IWC) and its Scientific Committee, Japan set an annual target of 333 minke whales for future hunts, down from some 900 under the previous programme.

Tokyo also defined the research period as 12 years from fiscal 2015 in response to the court's criticism of the programme's open-ended nature.

Japan killed 251 minke whales in the Antarctic in the 2013-14 season and 103 the previous year, far below its target because of direct action by conservationist group Sea Shepherd.

Tokyo also conducts hunts in the name of science in the Northwest Pacific, where it killed 132 whales in 2013, and off the Japanese coast, where it caught 92.

Despite widespread international opprobrium, Japan has continued to hunt whales using the scientific exemption, although it makes no secret of the fact that the meat from the creatures caught by taxpayer-funded ships ends up on dinner tables.