Manama, Bahrain (CNN) -- Human Rights Watch is urging Bahrain to stop special military court proceedings against those arrested during the country's anti-government's protests.
Most convictions were for patently political charges such as participating in unauthorized demonstrations and "incitement of hatred against the regime," and resulted in prison sentences ranging from one to five years, the group said Tuesday.
"Bahraini authorities should immediately halt all proceedings before the special military court and free everyone held solely for exercising their rights to free speech and peaceful assembly," the group said in a statement.
Those charged with genuine criminal offenses should be tried in an independent civilian court, it said.
Bahrain is one of several Middle Eastern and North African countries embroiled in anti-government protests. The ruling royal family -- Sunnis in a majority-Shiite nation -- accuses protesters of being motivated by sectarian differences and supported by Iran.
In recent days, the government began special military prosecutions of some of the protesters.
Human Rights Watch said these court proceedings violate international law.
"Most defendants hauled before Bahrain's special military court are facing blatantly political charges, and trials are unfair," said Joe Stork, deputy Middle East director at Human Rights Watch.
In a meeting with U.S. President Barack Obama last week, Bahrain's Crown Prince Salman bin Hamad al-Khalifa pledged he is seeking national dialogue with the protesters.
Bahrain's crackdown contradicts statements the prince made, Human Rights Watch said.
"The Crown Prince may be sincere in his efforts to promote dialogue, but what good is that while back home the government is crushing peaceful dissent and locking up people who should be part of the dialogue," Stork said.
As of Monday, 82 people have received verdicts from the military courts and 77 of them have been convicted. The sentences have ranged from five years in prison to life -- as well as two death sentences, the organization said.
Some of the trials have started without the lawyers or family members of the protesters being notified, Human Rights Watch said.
Bahrain is home to the U.S. Navy's Fifth Fleet, and the United States has been concerned about the instability in the Persian Gulf island state.
On Monday, the country put dozens of doctors and nurses on trial, accusing them of taking control of a hospital during anti-government protests, storing weapons and keeping people prisoner.
The doctors, their lawyers and international human rights activists say the defendants were tortured to extract confessions against a background of demonstrations in the kingdom.
On Sunday, at least two former Bahraini opposition lawmakers went on trial. Additionally, a military court sentenced a 20-year-old poet to a year in prison.
Matar Matar and Jawad Fairooz were charged with "spreading malicious lies in an attempt to overthrow the government," an official in the Information Affairs Authority told CNN.
Both men pleaded not guilty. The legal proceedings began Sunday without prior notice, according to a Matar family member who asked not to be named for security reasons.
Meanwhile, poet Ayat al-Qormozi, 20, was found guilty of assembling at Pearl Roundabout, the epicenter of anti-government demonstrations in the kingdom earlier this year. Additional charges included speaking out against Bahrain and the king.
The Bahrain Youth Society for Human Rights said she read a poem criticizing government policy at the Roundabout.
Her poem "caused incitement and hatred to his majesty the king and to the prime minister" with lines such as "we are people who kill humiliation" and "assassinate misery," said Sheikh Abdul-Aziz bin Mubarak of the country's Information Affairs Authority.
Amnesty International called the charges "unfair" in a statement after the sentence.
"By locking up a female poet merely for expressing her views in public, Bahrain's authorities are demonstrating how free speech and assembly are brutally denied to ordinary Bahrainis," said Malcolm Smart, Amnesty International's director for the Middle East and North Africa.
CNN's Jenifer Fenton contributed to this report.