Militant environmentalists Sea Shepherd fired distress flares at whaling ships in the Antarctic Ocean, the Japanese Fisheries Agency said Tuesday, in the latest high-seas confrontation.

Activists from the group's Bob Barker ship fired more than 40 flares and used laser lights against the Japanese vessels -- Yushin Maru No. 2 and No. 3 -- for a few hours on Monday evening, Japan time, the official said.

No damage or injuries were reported, he said.

The Sea Shepherd reported on its website that the incident was a "night attack" by the Japanese ships.

"Two harpoon vessels Yushin Maru No. 2 and Yushin Maru No. 3, turned and headed straight for the Sea Shepherd ship, Bob Barker," it said.

"The harpoon ships trained their spotlights on the bridge of the Bob Barker, in an effort to blind the crew but backed off when the Bob Barker crew retaliated with lasers."

"Flares were fired and angry radio messages exchanged in Japanese and English," it said.

Such exchanges have become increasingly routine between whalers and activists on the high seas.

Last month, anti-whaling campaigners attacked the Yushin Maru No. 3 by firing paint bombs and trying to jam its propeller with ropes, Japan's whaling body said.

Commercial whaling is banned under an international treaty but Japan has since 1987 used a loophole to carry out "lethal research" in the name of science.