The anti-whaling group Sea Shepherd says attempts by Japanese whalers to use pepper spray against protesters have backfired.
The Japanese government earlier accused the activists of injuring three crew members with stink bombs during the latest clash in Antarctic waters on Thursday.
But Paul Watson, captain of the Sea Shepherd vessel Steve Irwin, says video footage shows Japanese crew members aiming pepper spray at protesters in an inflatable boat. The footage shows the spray being blown back into the faces of the whalers, who reacted with pain.
Mr Watson says the whalers are becoming increasingly aggressive, having already sunk one Sea Shepherd boat this season and damaged another. He puts this down to whalers becoming frustrated at the hampering of their operations.
The Japanese government-funded Institute of Cetacean Research could not be reached for comment.
Mr Watson says the footage disproves Japanese government claims that the protesters were responsible for causing injuries with stink bombs. He says Sea Shepherd has an unblemished record of not hurting anyone in its 33-year history.
Japanese authorities say three sailors suffered facial injuries from stink bombs hurled by the activists on Thursday. Fisheries minister Hirotaka Akamatsu says the clash has left him furious.
During a five-hour confrontation, activists from the Sea Shepherd conservation group fired rancid butter, or butyric acid, at the whalers.
Both sides also sprayed each other with water cannon.
Japan says its sailors suffered minor acid-splash chemical injuries from the butyric acid, but Sea Shepherd denies anyone was injured in the incident, saying its stink bombs do not cause harm, even when they come in contact with the skin.
Sea Shepherd says its boat was trying to stop the Japanese fleet from entering the whale sanctuary when three Japanese boats attacked it with water cannon overnight on Thursday.
Mr Watson says the Japanese boats were the aggressors.
