Members of a marine mammal conservation group who attacked Japanese whalers off Antarctica on Friday, injuring two of them, are "terrorists," Japan's Fisheries Agency said.

Two activists from the Sea Shepherd protest ship went missing during the confrontation with Japanese whaling craft Nisshin Maru early Friday, but were rescued safely — with members of the Japanese whaling expedition assisting in the rescue efforts in the icy waters of the Ross Sea.

The protesters then resumed their pursuit of the Japanese vessel, and dumped foul-smelling butyric acid onto the whaling ship's deck, injuring two Japanese crewmembers, according to Takahide Naruko, the chief of the Far Seas Fisheries Division of the Fisheries Agency.

The two crewmembers suffered facial injuries when the bottle of acid smashed on deck, sending shards of glass in all directions, he said. One was hit by an empty container of acid and the other had acid squirted in his eye, he said.

The protesters then resumed their pursuit of the Japanese vessel, and dumped foul-smelling butyric acid onto the whaling ship's deck, injuring two Japanese crewmembers, the Fisheries Agency said in a statement.

National broadcaster NHK said the protesters also threw a smoke bomb and that the two crewmembers suffered facial injuries when the bottle of acid smashed on desk, sending shards of glass in all directions.

Neither of the Japanese crewmen hurt in the incident suffered life-threatening injuries, according to Hideki Moronuki, the assistant director of the agency's whaling department, although he declined to give details.

"They're terrorists," Moronuki said of the anti-whaling activists who had been searching for the Japanese fleet for weeks. "They must stop these dangerous acts immediately."

He said the Sea Shepherd attack was unforgivable especially given that the Japanese helped find the missing protesters.

"We rescued them from a humanitarian point of view, but they attacked the Japanese as soon as they were safe," Moronuki said, saying the attack returned "good for evil."

Japan is considering what measures to take, including a possible lawsuit against the group, he said.

The Nisshin Maru left Japan in November for a six-month whaling expedition in the Antarctic as part of a scientific whaling program conducted within the rules of the International Whaling Commission.

Tokyo maintains that whaling is a national tradition and a vital part of its food culture, and is pushing for a limited resumption of hunts, arguing that whale stocks have sufficiently recovered since 1986 when a global moratorium on commercial whaling was introduced.

Sea Shepherd "successfully delivered" six liters of butyric acid to the ship's flensing deck, where whales are cut up, halting the crew's work, the group said on its Web site Friday.

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