Environmentalists chasing a Japanese whaling fleet off Antarctica have thrown “stink” bombs at one of the vessels.

The US-based environmental group Sea Shepherd said the Japanese ship, the Kaiko Maru, was spotted by its vessel the Steve Irwin north of Mawson Peninsula.

“The Sea Shepherd crew pursued and delivered 10 bottles of rotten butter and 15 bottles of a methyl cellulose and indelible dye mixture,” it said in a statement on its website, which was dated Friday.

“That is one stinky slippery ship,” Sea Shepherd’s Peter Hammarstedt said.

The Japanese Fisheries Agency said no one was hurt and the Japanese vessel was not damaged during the incident which lasted about three hours, Kyodo news agency reported.

Japan’s whaling fleet is in the Antarctic for an annual hunt. Despite an international ban on whaling, Japan justifies the hunt on the grounds this whaling is for “scientific” purposes.

Much of the meat ends up on supermarket shelves.