A German court Wednesday reissued an arrest warrant for the extradition to Costa Rica of Paul Watson, founder of marine conservation group Sea Shepherd, who had skipped bail and left the country.

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

Earlier this year, Costa Rica filed an extradition request on charges stemming from a high-seas confrontation between a Sea Shepherd ship and a Costa Rican vessel over alleged illegal shark finning in 2002.

Watson, a Canadian national who leads the Sea Shepherd organisation noted for its aggressive attacks on Japanese whalers, was accused of "putting a ship's crew in danger".

The 61-year-old, whom Sea Shepherd members affectionately call "the captain" -- and who looks the part with a thick shock of white hair and beard -- was arrested at Frankfurt airport in western Germany in May.

He was detained for a week before being released on bail after paying 250,000 euros ($303,500) and ordered to appear before police twice a day.

He has not adhered to the terms of his bail however since July 22, the court said on Wednesday.

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

A spokeswoman for the German federal justice ministry said it was not aware of Watson's whereabouts, nor could it say whether he was still in the country.

In an interview with AFP after he was arrested, the activist vowed that his campaign would continue even if he were tried and jailed.

"They hope that by getting me out of the way, they'll shut down our operations. They won't," Watson said.

"This is not about me. It is about our oceans and the ever-escalating threat of diminishment of the diversity of life in our seas. It is about the sharks, the whales, the seals, the sea turtles and the fish," he said.

On a visit to Germany in May, Costa Rican President Laura Chinchilla said Watson would have a fair trial if extradited to the Central American country.

The Canadian national is well known for his pursuit and harassment of Japanese whaling boats off Antarctica, which in recent years has significantly reduced the number of animals slaughtered.

This year the group hurled stink bombs at the boats on the high seas and used ropes to try to tangle their propellers in a series of exchanges that saw the whalers retaliate with water cannon.

He has previously suggested that Japan might be "putting pressure" on Germany to carry out the extradition order.

Watson has said he believed it is unusual to issue an extradition order for "a relatively minor offence, where no one was injured and no property damaged."

The 2002 confrontation occurred in Guatemalan waters when a Sea Shepherd vessel filming a movie encountered a Costa Rican ship that it said was illegally harvesting shark fins.

Sea Shepherd claimed that it then attempted to escort the Costa Rican ship back to port. The crew accused the activists of trying to kill them, allegations Sea Shepherd denies. Costa Rica then sought to charge Watson with endangering the crew.