Greenpeace has described the arrest of activists for protesting against drilling in the Arctic as a "circus" after a court ruling extended the detention in Russia by months.
A court in St Petersburg said Australian Colin Russell, one of the so-called Arctic 30, could remain in jail until at least February while investigations continue.
He was one of 28 activists and two freelance journalists arrested two months ago after their ship was seized by Russian security authorities.
Further court hearings are planned to hear applications for an extension to the detentions.
Greenpeace International Executive Director Kumi Naidoo said: "The authorities say they need three months more to investigate an imaginary offence over which they have no jurisdiction.
"They say they need to keep those brave men and women in jail until February so they can probe a crime that simply did not happen.
"This case is now a circus. Our friends may now be in jail for months longer, all because they made a stand for all of us in the pristine Arctic.
"We will continue to pursue every legal avenue we can, and leave no stone unturned, until each and every one of them is home with their families.
"We hope the International Tribunal for the Law of the Sea will order their release when they adjudicate on Friday."
Before being told he must remain in prison, Colin Russell told the judge: "I haven't done anything wrong.
"I don't understand the reasons why I've been detained. I've done two months' hard time for nothing."
Six Britons were among those detained, including journalist Kieron Bryon, who is due in court later today.
John Sauven, Greenpeace's executive director, said: "The decision by the Russian court to extend the remand of the first of the Arctic 30 to another three months imprisonment, without trial, is turning the legal process into a sham.
"If the court applies this extension to all of our activists, they will have done five months without being convicted of anything. The 30 presently being held are neither pirates nor hooligans and it is time prosecuting authorities recognised what has become obvious to the world - that what they're doing bears no resemblance to justice."