Japanese whalers returned to port Saturday after a four-month voyage to waters around Antarctica for their annual winter cull.

The arrival of the 8,145-ton mother vessel Nisshin Maru and two smaller ships at Shimonoseki, Yamaguchi Prefecture, came after the International Court of Justice ruled Monday that Japan's whaling is not conducted for scientific purposes and ordered a halt.

The Fisheries Agency said the whalers' activities this winter were again hampered by the U.S.-based anti-whaling group Sea Shepherd.

Japan, which has conducted what it calls "scientific" whaling in the Antarctic Ocean since 1987, had insisted that the program is consistent with a 1946 international convention that permits research whaling.

Australia lodged the case to end Japanese whaling in the Antarctic Ocean with the International Court of Justice in The Hague, arguing it was a cover for commercial whaling in violation of obligations under the convention.

A moratorium on commercial whaling came into force in 1986.