A German court has called for the extradition to Costa Rica of Paul Watson, the founder of marine conservation group Sea Shepherd, as he had skipped bail and apparently left the country.

The higher regional court in Frankfurt said Watson's lawyer had informed them he had left Germany "for an unspecified destination" and that they had therefore decided to resume extradition proceedings against him.

Watson, a Canadian national, was held in custody for more than a week in May as investigators examined charges against him that stemmed from a confrontation in Costa Rica in 2002.

The activist was detained at Frankfurt airport after Costa Rica issued an international arrest warrant.

Authorities in Costa Rica allege Mr Watson's crew aboard Sea Shepherd's Ocean Warrior ship endangered a fishing vessel during a confrontation off Guatemala's coast in 2002.

"Since by fleeing, Watson has shown that he cannot justify the trust placed in him, the extradition process has been restarted," the court said.

Sea Shepherd, which has clashed with Japanese whalers in the Southern Ocean, prides itself on "innovative direct-action tactics" to confront so-called illegal activity on the high seas - including the use of acoustic weapons, water cannon and stink bombs against whalers.

The not-for-profit group has also trailed seal hunters and fought campaigns for sharks and dolphins, as well as regularly patrolling the Galapagos Islands.

In 2010 it clashed violently with Japanese boats, leading to the sinking of Sea Shepherd's high-tech superboat boat Ady Gil in the remote Southern Ocean.

AFP