The group of Greenpeace activists arrested in Russia during a protest against drilling in the Arctic face a three-month extension to their detention.
The organisation said Russia's investigative committee had announced it was applying for the extension against the 28 campaigners and two freelance journalists while it continues its investigations.
Greenpeace International executive director Kumi Naidoo said: "Our hearts break for our friends in jail and for their loved ones on the outside.
"We will fiercely resist this absurd attempt to keep those men and women in jail for a crime they did not commit. If the authorities succeed then we will appeal and ask for their release as soon as the court can schedule a hearing. This is a farce, it is an outrage that makes a joke of justice. It's time for the Arctic 30 to come home."
Greenpeace said hearings over the extension bid must be completed by November 24.
Videographer Kieron Bryan, 29, engineer Iain Rogers, 37, and Alexandra Harris, 27, all from Devon, are among the group who were held when armed Russian officials boarded the Arctic Sunrise in September.
Sir Paul McCartney has written a personal letter to Russian president Vladimir Putin calling for the release of Greenpeace activists.
