A Bahraini civilian court on Tuesday upheld sentences of up to life in prison against the leaders of last year's uprising.
It is a decision that could dim prospects for defusing persistent unrest and advancing reform in the important US ally against Iran.
Bahrain, where the US Fifth Fleet is based, has been in political turmoil since a protest movement dominated by majority Shia Muslims erupted in February 2011 during a wave of revolts against authoritarian governments across the Arab world.
A Bahraini civilian court on Tuesday upheld sentences of up to life in prison against the leaders of last year's uprising
The Sunni Muslim ruling Al Khalifa family put down the uprising with martial law and the aid of troops from Gulf neighbours Saudi Arabia and the United Arab Emirates, but unrest later resumed with daily clashes between Shias and police.
"All the accused are guilty in the case of taking part in a conspiracy to overturn the system of government, contacts with foreign bodies and violation of the constitution," the state news agency BNA said, referring to them as a "terrorist group".
The verdicts, originally issued by a military court against 21 men, including seven in absentia, comprise eight life sentences. Thirteen remain in jail after one was released. Defence lawyers said Tuesday's ruling could be appealed.
Opposition activists fear Bahraini authorities want to prolong the case and hold on to the men as bargaining chips in an eventual resolution to the conflict. The government says courts in the Gulf monarchy are independent.
The authorities have initiated low-level talks with opposition groups, but said they must do more to stop street violence. The opposition says this stance is a ruse to avoid concessions and they are not responsible for clashes.
Jane Kinninmont, a Chatham House analyst based in London, said the verdict sent a tough message to protesters as well as Western countries who have tried to persuade Manama to compromise with the protest movement.
"The authorities may be trying to show their strength ahead of a planned dialogue with political societies," she said, adding that could backfire if protests and clashes escalate.
"This may also send a message to the international community about the limits of pressure. Strong Saudi backing for Bahrain has made it less interested in what the West has to say."
Though US officials are keen for a release of Bahraini prisoners to help restore calm, Washington has avoided irritating Manama by calling publicly for their release.
The presence of US warships helps ensure a free flow of oil exports out of the Gulf, which Iran has threatened to blockade if the stand-off with Western powers over its nuclear energy programme deteriorates into confrontation.
Danish Foreign Minister Villy Sovndal said the verdict was disappointing and called for the release of Abdulhadi Al Khawaja, a rights activist in the case with Danish nationality.
"It is important that the international community continue to make Bahrain aware of the importance of the country respecting basic human rights," Sovndal said in a written comment.
Eight of the 20 men received life sentences in a military court last year, including Al Khawaja and opposition leader Hassan Mushaimaa, who supported making Bahrain a republic.
Ibrahim Sharif, leader of the opposition Waad party and the only Sunni among the 20, is serving a five-year sentence while blogger Ali Abdulemam was given a 15-year term and is in hiding.
"I am very disappointed. This was a shock to people," said Hussein Jawad, son of Mohammed Jawad, who is serving a 15-year sentence. "If they don't want life or a future for Bahrain, they will keep the verdicts like this."
Sunnis, who fear the rise of Shia Islamists if the government compromises with opposition demands for political reform, praised the ruling. "God is great! God is great!" wrote cleric Mohammed Khalid on Twitter.
حجر بن عدی کی نبش قبر اجماع مذاہب اربعہ کے بر خلاف کی گئی/ شام اور بحرین کے شیعوں کے حق میں دعا کرنا سب کی ذمہ داری
(Most influential bahrainies persons of year 2012)
