Activists of antiwhaling group Sea Shepherd Conservation Society on Sunday obstructed Japan's so-called research whaling in the Antarctic Ocean, hurling a rope at a whaling ship and twisting it around the ship's propeller, the Japanese Fisheries Agency said.

The activists also threw bottles containing butyric acid and hurled smoke candles at the Yushin Maru No. 2 during the incident which started at 7:20 a.m. and lasted for about two hours, the agency said.

The ship slowed down consequently, although none of its crew was injured, according to the agency.

The ship counteracted the Sea Shepherd actions by spraying water and issuing warnings, it added.