Bahraini rights activist Nabeel Rajab, a leader of protests against the authorities in the Gulf kingdom, is to be detained for one week for "insulting a statutory body," his lawyer told AFP on Sunday.
"The representative of the public prosecutor has ordered his detention for seven days for insulting a statutory body via Twitter," Mohamed al-Jishi said, referring to what activists said were tweets criticising the interior ministry.
Jishi said Rajab denied the charge, saying it "aims at hindering my rights work and my right of expression."
Rajab, who heads the non-governmental Bahrain Centre for Human Rights (BCHR), was arrested at the airport late on Saturday, the centre said.
"Nabeel Rajab arrested by order of public prosecution. All legal procedures are being taken," the interior ministry said on its own Twitter account.
Rajab was returning from Lebanon after meeting the representative of the UN High Commissioner for Human Rights, said activist Mohammed al-Maskati, who travelled with him.
He was led away by people in plainclothes, Maskati tweeted.
Earlier on Sunday, Rajab appeared in court in Manama on separate charges -- "participating in illegal assembly and calling others to join," Jishi said. The next hearing in this case will be on May 22.
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A BCHR statement quoted Rajab as saying earlier that he refused to attend the trial, accusing the system of unfairness.
"Given that Bahrain in essence lacks a judiciary system that is independent and/or fair, and is far from being in line with international standards of a fair trial, I have decided to boycott the trial against myself," he said.
"The judiciary system in Bahrain, today, is a tool used against human rights defenders and people calling for democracy and justice," he added.
The International Federation for Human Rights (FIDH) called in a statement "for the immediate and unconditional release of Rajab and other human rights defenders, as this judicial harassment against them seems to be solely aimed at sanctioning their human rights activities."
The kingdom's largest Shiite opposition formation Al-Wefaq condemned Rajab's arrest as "illegal."
The activist, a member of Bahrain's Shiite majority, has had various standoffs with police as he led protests in Manama calling for democratic change in the Sunni-ruled kingdom.
In one he claimed to have been beaten by riot police.
Rajab has insisted on demonstrating inside the capital, unlike the main Shiite opposition which now stages its protests in Shiite villages, after last year's crackdown on protesters who occupied Manama's Pearl Square for a month.
Amnesty International says 60 people have been killed since protests erupted in Bahrain in February 2011.