Greenpeace is describing an attempt to detain 30 of its activists in a Russian prison for a further three months as a farce.
The group, including New Zealanders Jonathan Beauchamp and David Haussman, were arrested in September after protesting against oil exploration in the Barents Sea.
They were moved this month from the northern port of Murmansk and are now being held in St Petersburg.
Their ship, the Arctic Sunrise, remains under detention in Murmansk.
Russia's Investigative Committee is in the process of applying to the courts to extend their incarceration so it has more time to investigate their alleged crimes.
It has until the end of next week to be granted the extension, otherwise the activists will be released.
The application will be made in front of a judge in St Petersburg next week.
Greenpeace spokesperson Kumi Naidoo says the group will resist this attempt to keep the activists in jail for a crime they did not commit.