A Japanese whaling ship joined in the search for two anti-whaling activists who went missing during a confrontation in icy seas off Antarctica.

A temporary truce was called during a joint, eight-hour search for the two members of the conservation group Sea Shepherd, who were later recovered.

The pair became lost during a clash in which the activist group splashed acid onto the deck of the whaling ship. The Japanese government called the actions “piratical” and “dangerous”.

The incident happened last week, after the activist ship The Farley Mowat caught up with Japan’s Nisshin Maru whaling ship. The US-based Sea Shepherd group said its activists managed to douse the deck of the whaler with six litres of non-toxic but foul smelling butyric acid.

During the confrontation, US activist John Gravois and Australian activist Karl Neilsen became lost in the heavy fog and snow. Gravois later told the Australian Associated Press that their inflatable dinghy was damaged after it collided with the whaling ship and they quickly fell behind the group.

He said they managed to tie their boat to an iceberg to stop themselves from drifting, while they awaited rescue. “When they found us it was a feeling of the most extreme relief that you can image,” he said.