Antiwhaling activists hurled containers of rotten butter at a Japanese whaling ship in Antarctic waters March 3, lightly injuring several crew members and triggering a protest from Tokyo, the government said.

Protesters aboard a boat operated by the antiwhaling group Sea Shepherd threw the bottles — containing butyric acid, produced by rotting butter — at the Nisshin Maru whaling ship, which is conducting Japan's research whaling program.

"We strongly condemn this," Chief Cabinet Secretary Nobutaka Machimura said. Japanese officials said at least three crew members were injured lightly, apparently by the burning sensation caused by the odor of the acid.