Several thousand Bahrainis marched near the capital Manama on Friday to demand reforms in a protest called by the Shiite opposition in the tiny but strategic Sunni-ruled Gulf kingdom, witnesses said.
The demonstrators also called for the departure of the king's uncle Sheikh Khalifa bin Salman al-Khalifa, who has been prime minister for more than four decades.
Thousands of men and women protested in Al-Bilad al-Qadim, waving Bahraini flags and brandishing pictures of political detainees, the witnesses said.
"National action calling for democratic change will not stop ... until all rights have been granted," opposition groups said in a statement.
"The action of the people of Bahrain on the ground has lasted for two years and will not end -- the opposition will act every day with demonstrations until all our demands are met," it added.
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Referring to a call by King Hamad on January 23 for a new round of national dialogue, the statement said "this dialogue is obscure and does not reflect a serious will on the part of the authorities to meet popular demands."
Bahrain, ruled by the minority Sunni Al-Khalifa dynasty, has been rocked by Shiite-led protests since February 2011.
Despite a bloody crackdown on protesters in Manama between mid-February and mid-March that year, sporadic demonstrations have continued in villages around the capital.
The International Federation for Human Rights says 80 people have died since the start of the Arab Spring-inspired uprising on February 14, 2011.
Bahrain is home to the US Fifth Fleet and strategically situated across the Gulf from Shiite Iran.