Amnesty International on Monday urged the United Arab Emirates to "immediately" release 10 men who it said were being arbitrarily detained beyond their jail sentences.
They were being kept in detention "on the pretext of 'counter-extremism counselling'", according to Amnesty.
The 10 UAE citizens were among 69 nationals arrested in 2012 and jailed in 2013 for up to 15 years on charges of plotting to overthrow the government.
They belonged to a group of 94 defendants, including 13 women.
Prosecutors said the accused were linked to Al-Islah, a group with ties to the Muslim Brotherhood, which the UAE categorises as a terrorist organisation.
"These men have already spent a decade behind bars for daring to speak out against the Emirati authorities or being perceived as political opposition, and now this injustice is being prolonged past their long-awaited release dates," Amnesty's Middle East and North Africa deputy director Lynn Maalouf, said in a statement.
"UAE authorities must immediately release anyone detained beyond the completion of their prison sentence, and cease the unlawful practice of arbitrarily extending prison terms."
Amnesty International condemned the verdicts at the time as "grossly unfair" and the charges as "bogus".
The Federal Supreme Court sentenced 56 of the 94 defendants to 10 years in prison each, the official WAM news agency reported at the time.
Five defendants were jailed for seven years each, while eight tried in absentia were sentenced to 15-year terms, it said.
A total of 25 people were acquitted including all 13 women arrested in the crackdown.
Their trial was the largest in the history of the UAE.