The campaigner, who helped to document the slaughter in Taiji in controversial 2009 documentary The Cove, was stopped by police in Nachikatsuura after authorities received a tip off suggesting the 75 year old may have been driving under the influence of alcohol.

He passed a breath test, but he was subsequently taken into custody for not carrying his travel documents or another form of identification - a violation of Japan's laws for visitors.

O'Barry was released on Tuesday (01Sep15), although it is not yet known if he will face any charges.

He is among a group of activists who have gathered in Taiji in a bid to halt the bloody six-month hunting season, during which fishermen lure dolphins into a cove for capture or slaughter. The hunt had been due to kick off on Tuesday (01Sep15), but was postponed due to bad weather.

The Cove won director Louie Psihoyos the Academy Award for Best Documentary Feature in 2010.