Human rights abuses remained widespread last year in the Gulf states, including discrimination against dissidents, migrant labourers, women and religious minorities, Amnesty International said in a report on Wednesday.
In particular, authorities severely restricted freedom of speech, association and assembly and clamped down on the dissent and unrest that swept several countries during the so-called Arab Spring, the London-based group said.
Arbitrary arrests of critics and opposition members were commonplace in almost all the Gulf states and accompanied with long periods of detention without trial, it said.
In Saudi Arabia, "government critics and political activists were detained without trial or sentenced after grossly unfair trials," Amnesty said.
Saudi authorities continued to clamp down on people calling for political and other reform as well as human rights defenders and activists. Some were detained without charge or trial, and others faced prosecution on vague charges such as "disobeying the ruler."
The Saudi authorities continued to hold incommunicado thousands of suspected members and supporters of Al-Qaeda and other Islamist groups. And a number of their relatives were detained when they staged a protest to call for their release.
Women were discriminated against in the Gulf states in law and practise and inadequately protected against domestic and other violence, it said.
In Saudi Arabia, women continued to be denied the right to drive despite several campaigns by activists.
Amnesty said migrant workers in the Gulf states were inadequately protected by labour laws and vulnerable to exploitation and abuse by employers. Women domestic workers in particular were at risk of sexual violence and other abuses.
Foreign workers and their families are estimated to be around 17 million out of a native population of around 40 million, according to unofficial estimates.
Hundreds of people were on death row at the end of last year with many executions reported. Most were in Saudi Arabia, where 79 people were beheaded in 2012, the report said.
The Amnesty report spoke of discrimination against Shiite Muslims who form a minority in Saudi Arabia and majority in the Sunni-ruled Bahrain, and which have been witnessing violent protests by Shiites for more than two years.
Security forces in the two nations were alleged to have used excessive force at times against the protesters. At least 10 people were shot dead during protests in the Saudi oil-rich Eastern Province where the majority of Shiites live.
In neighbouring Bahrain, dozens of protesters and policemen were reported killed and many wounded during protests.
In the United Arab Emirates, Kuwait and Oman hundreds were arrested and put on trial for protesting and some sentenced to prison terms. In Qatar, a poet was handed a lengthy jail term for allegedly insulting the ruler.