Police in Bahrain arrested the head of the banned Shiite opposition movement Al-Wefaq on Sunday after he had been called in for questioning, his party said.
After Sheikh Ali Salman's party announced his arrest, clashes broke out between security forces and hundreds of Al-Wefaq supporters gathered at his house in the Shiite village of Bilad al-Qadim near Manama, witnesses said.
Police used tear gas and birdshot to disperse the crowds protesting against Salman's arrest, the witnesses said. There was no immediate news of casualties.
Salman had been summoned to the criminal investigation department on Sunday morning and questioned about "violating certain aspects of the law", an interior ministry statement said earlier.
It provided no further details.
Al-Wefaq's statement said Salman was arrested after a lengthy interrogation at the ministry by police.
His lawyer, Abdullah al-Shamlan, tweeted that Salman had been accused of "inciting hatred against the regime and calling for its overthrow by force".
He said he had not been allowed to attend his client's questioning.
Shamlan said the Al-Wefaq chief was also accused of "insulting the judiciary and the executive branch", of "sectarian incitement", of "spreading false news likely to cause panic and undermine security" and "participation in events detrimental to the economy".
Al-Wefaq demanded the immediate release of its leader, calling his detention "a dangerous adventure that will complicate the political situation in Bahrain".
- Security barricades -
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It said he had been detained for more than 10 hours "for the sake of investigation for false accusations against him".
The party statement denounced the security forces for erecting barricades outside several Shiite villages, mainly on roads leading to the Al-Wefaq headquarters in a Manama suburb.
Salman, 49, secured a new four-year term as Al-Wefaq chief at its general congress on Friday.
The same day thousands of Shiites protested along a road linking two of their villages near Manama to call for the dismissal of parliament and the government.
In July, the justice ministry sued Al-Wefaq, demanding that it rectify its "illegal status following the annulment of four general assemblies for lack of a quorum and the non-commitment to the public and transparency requirements for holding them".
The Manama administrative court slapped Al-Wefaq with the ban on October 28 and gave it three months to hold an assembly to elect its leadership.
The ruling came after Al-Wefaq announced it was boycotting a parliamentary election in November, the first in the Gulf state since Sunni authorities crushed Shiite-led pro-democracy protests in 2011.
Al-Wefaq, which withdrew its lawmakers from parliament in protest, condemned the vote as a "farce".
It has called for an elected prime minister who is independent from the ruling royal family.
Bahrain, home base of the US Navy's Fifth Fleet, is ruled by the Sunni Al-Khalifa dynasty but the population is majority Shiite.
In 2011 the authorities crushed a month-long pro-democracy protest led by the opposition, but protests continue in Shiite villages outside the capital.
At least 89 people are estimated to have been killed in clashes with security forces, and hundreds have been arrested and put on trial since the uprising.