TOKYO: Japan said on Wednesday that it had long been pushing countries to arrest anti-whaling activist Paul Watson, who is in custody in Greenland facing possible extradition.

Police in the autonomous Danish territory arrested Watson, the American-Canadian founder of activist group Sea Shepherd, on Sunday under an Interpol "red notice" issued by Japan.

The 73-year-old is to remain in custody until Aug 15, while the Danish justice ministry must decide on whether he should be extradited to Japan.

"Japan has long been making the necessary efforts to the relevant countries' authorities," spokesman Yoshimasa Hayashi told reporters in the government's first comments on Watson's arrest.

"In any case, we understand that the Japan Coast Guard, which continues to investigate this matter, will take appropriate action in consultation with the relevant ministries," he said.

French President Emmanuel Macron's office said on Tuesday he was pressing authorities in Denmark, a fellow member of the European Union, not to extradite Watson.

An online petition in France for Macron to call for Watson's release has gathered almost 475,000 signatures, including celebrities such as film star and animal rights activist Brigitte Bardot.

The red notice was issued in 2012, with an Interpol statement at the time saying Watson was wanted by Japan on charges of causing damage and injury against a Japanese whaling ship in the Antarctic Ocean two years earlier.

At the time Japanese ships, pursued aggressively by activists, hunted whales in the Antarctic and North Pacific for "scientific" purposes.

Japan now conducts whaling only inside its territorial waters and exclusive economic zone, going after Bryde's, minke and sei whales.

The Captain Paul Watson Foundation (CPWF) said on Monday that the arrest was a "surprise since the Foundation's lawyers had reported that the Red Notice had been withdrawn".

CPWF said the ship John Paul DeJoria was en route to the Northwest Passage on its way to intercept Japan's newly built factory ship, the Kangei Maru, in the North Pacific when Watson was arrested.

The Kangei Maru, a 9,300-tonne "mothership" that set off from Japan in May, processes whales caught by smaller vessels and stores their meat for later consumption in Japan.

However, the CPWF said it suspects Japan will use its new ship to resume high-seas whaling in the Southern Ocean and North Pacific by 2025.

 - AFP