Prosecutors in Sunni-ruled Bahrain charged Shiite opposition chief Sheikh Ali Salman on Monday with promoting regime change in the Gulf kingdom through hatred and violence.
The prosecution said Salman, whose detention on Sunday triggered ongoing clashes between protesters and police, will remain in custody for further questioning on Tuesday.
Salman has been charged with "promoting regime change by force, threats and illegal means and of insulting the interior ministry publicly", prosecutor Nayef Mahmud said in a statement.
He was also accused of inciting people to break the law and "hatred towards a segment of the people", an allusion to Sunni Muslims who are a minority in the Shiite-majority kingdom.
The prosecutor said police also suspect Salman of calling for foreign interference by "urging super powers to intervene in Bahrain to support him in his bid to change the regime".
He did not say what powers he was referring to.
Salman heads the main opposition group Al-Wefaq. News of his arrest Sunday brought hundreds of his supporters onto the streets of Shiite villages outside Manama, leading to clashes with security forces.
Police fired tear gas and birdshot to disperse the protesters, many of whom had gathered in Salman's home village of Bilad al-Qadeem, witnesses said.
There were also clashes on Monday afternoon.
- 'Inciting hatred and violence' -
Speaking Monday about the arrest, Information Minister Isa Abdulrahman al-Hammadi said Salman has been interrogated primarily about suspected "breaches of the law, including inciting hatred and violence".
Authorities have been tight-lipped about Salman's whereabouts.
The prosecutor said four lawyers were allowed to meet him in private on Monday and also to sit in on his interrogation.
Hammadi said "the government of Bahrain supports the right to free speech, which is protected by the constitution, but no country and no government can allow hate speech to go by unchecked".
He warned that any escalation of violence will be dealt with "in accordance with the law in Bahrain" where authorities clamp down on unauthorised protests.
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A statement from opposition groups led by Al-Wefaq called Salman's detention "an escalating step that targets social stability and civil peace in Bahrain".
Authorities are "moving backward to a police state instead of taking steps towards a political solution and an end to serious human rights violations against citizens".
Al-Wefaq has demanded Salman's immediate release, and several rights groups have also condemned his arrest.
Top Shiite clerics issued a statement late Sunday criticising Salman's questioning as a "huge insult to the whole people".
- 'Not a wise move' -
Four leading clerics, including Isa al-Qassem, considered to be Al-Wefaq's spiritual leader, said calling him in does not demonstrate "wise political reasoning".
They also warned that harming Salman would amount to "harming the whole population".
Bahrain has been gripped by sporadic violence ever since the authorities crushed month-long protests led by Al-Wefaq in 2011.
At least 89 people have been killed since then in clashes with security forces, and hundreds have been arrested and put on trial, human rights groups say.
Strategically located just across the Gulf from Iran, Bahrain is home base of the US Navy's Fifth Fleet, and Britain announced plans earlier this month to build a naval base of its own there.
Bahrain is also a partner in the US-led coalition carrying out air strikes against the Islamic State group in Syria.
Authorities have rejected Al-Wefaq's demand for an elected prime minister to replace the current government dominated by the ruling family.
Al-Wefaq's announcement that it would boycott a November parliamentary election it dismissed as a farce was followed by a court order banning the party in late October.
Salman, re-elected as party leader on Friday, marked the occasion by leading a protest march outside the capital.
In other developments on Monday, a Manama court sentenced two Shiites to death and a third to life in prison for killing a policeman, BNA state news agency said.
Nine others were jailed for six years for their involvement in the explosion that killed him.