An incendiary device fired by anti-whaling activists Sea Shepherd burns in the bow deck of Japanese whaling research ship Nisshin Maru in the Southern Ocean in this handout photo taken and released by the Institute of Cetacean Research February 9, 2011. Obstructions by the hardline anti-whaling group has forced Japan to cut short its Antarctic whale hunt, Fisheries Minister Michihiko Kano said on February 18, 2011, the first time the fleet is heading home early due to clashes with activists. [Photo/Agencies]

TOKYO - The Japanese government on Friday announced it is ending its whaling season early due to persistent disruptions from anti-whaling activists.

"We've decided to wind up our research whaling unavoidably from the viewpoint of securing the safety of the crew and the boats," Japan's Farm and Fisheries Minister Michihiko Kano said, adding that the whaling fleet will return to Japan shortly.

Japan had said it had suspended its hunt on February 10. Usually the season continues until mid-March.

The Sea Shepherd Conservation Society says one of its boats has been blocking the main ship, Nisshin Maru's stern loading ramp, preventing any harpooned whales from being loaded on to the ship.

Japan's whaling fleet involves 180 people on working on four ships. During the southern winter season they aim to kill upwards of 945 whales in Antarctic waters, officials said.

Sea Shepherd ships have been chasing the Japanese fleet for weeks in the icy seas, trying to prevent the whalers from filling their seasonal quota

Commercial whaling was banned in 1986 but Japan uses a regulation permitting hunting for scientific research. Some anti- whaling environmentalists maintain that this is simply Japan's way of exploiting a loophole for the continuation of commercial whaling.