Anti-whaling activist Paul Watson has been released from prison in Greenland where he spent five months in custody, after Denmark rejected a Japanese request to extradite him.

Mr Watson, 74, was detained by police when his ship docked in Greenland's capital, Nuuk, last July.

Police had acted on a 2012 Japanese warrant that accused him of causing damage to a Japanese whaling ship, obstructing business and injuring a crew member during an encounter in Antarctic waters in February 2010.

Mr Watson, who is a Canadian-American citizen and featured in the reality TV show Whale Wars, had denied any wrongdoing.

Whaling and eating whale meat have been heavily criticised by conservation groups, but officials in Japan argue that it is part of the country's culture and way of life.

The Danish justice ministry confirmed that it would not be complying with the Japanese extradition request, basing its decision on "the nature of circumstances" as well as the fact that the incident dated back 14 years.

His lawyer Julie Stage told the AFP news agency that he was now free.

As Greenland is an autonomous territory of Denmark, the decision on his extradition was made in Copenhagen. Although Japan and Denmark have no extradition treaty, the government in Tokyo had asked Denmark to hand him over.

Denmark's justice minister, Peter Hummelgaard, said it had been of "central importance" to ensure that the length of time Mr Watson had been detained in Greenland would be deducted from any possible prison sentence he may have later faced in Japan.

He added that the ministry concluded "it cannot be assumed with the necessary certainty that this will be the case" after correspondence with Japanese authorities.

Mr Watson's vessel, called the M/Y John Paul DeJoria, had been heading to the North Pacific with a crew of 26 volunteers on board, in a bid to intercept a new Japanese whaling ship when it docked to refuel in Nuuk on 21 July.

At a previous custodial hearing, Mr Watson told the court that the case was "about revenge for a television show that extremely embarrassed Japan in the eyes of the world".

For years he has been a controversial figure known for confrontations with whaling vessels at sea.

The campaigner is the former head of Sea Shepherd Conservation Society, which he left in 2022 to set up the Captain Paul Watson Foundation.

Japan withdrew from the International Whaling Commission and resumed commercial whaling in 2019, after a 30-year hiatus. However, it continued whaling for what it said were research purposes.