A Gulf rights group has called for the release of thousands of prisoners of conscience in the oil-rich Gulf states as it marked what it called Gulf Detainees Day to highlight their plight.
The Gulf monarchies do not allow political parties and criticism of rulers can easily land someone in jail.
"We call for the release of prisoners and detainees who have been put behind bars for simply expressing their opinion," Anwar al-Rasheed, head of the Gulf Forum for Civil Societies, said Thursday night.
Rasheed said there are "between 30,000 and 40,000 opinion prisoners and detainees," in the six-nation Gulf Cooperation Council, which groups Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and United Arab Emirates.
He said the numbers are based on data compiled by Gulf rights activists, international organisations and rights groups.
The overwhelming majority of the prisoners are held in Saudi Arabia followed by Bahrain, Rasheed said.
Rasheed said his group has arranged with a number of lawyers from Europe and the United States to form a legal team to visit prisons in Gulf states when governments allow it.
The detainees include doctors, teachers, writers, parliamentarians, activists, politicians and others, according to the group.
Rasheed even spoke of cases in which prisoners have remained in jail even after serving their terms. In other instances, he said people have been stripped of their basic rights, including a ban on travel, after they were released.
Last October, rights group Amnesty International accused Saudi Arabia of "arbitrary arrests and detention, unfair trials, torture and other ill-treatment over the past four years."
This March, it said "prisoners of conscience" in Bahrain were still behind bars three years after a month-long Shiite-led uprising was crashed by security forces.
And this week, it said prominent UAE human rights lawyer Mohammed al-Roken, was in solitary confinement and risks torture.
Roken was one of 69 people jailed for 15 years last July for plotting to overthrow the regime. A total of 94 people were tried, 13 of them women.