Bahrain on Sunday extended by two weeks the period of detention for prominent rights activist Nabeel Rajab, accused of spreading false news, for the second time this month.
Rajab's family say he was arrested on April 2 for posting comments on Twitter denouncing alleged torture in a prison where Shiite activists are held.
The prosecution "ordered that he remain detained for 15 days" pending the results of further investigation, the official BNA news agency reported.
Shiite-majority but Sunni-ruled Bahrain first extended Rajab's period of detention by 15 days on April 11.
A prosecution service statement said the Shiite activist was accused of "spreading tendentious rumours" about the Gulf state's participation in the Saudi-led Arab coalition waging an air offensive against Shiite rebels in Yemen, and "attacking a state institution".
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It accused him of posting online "edited footage from television broadcasts on events in Syria and Palestine, unrelated to military operations in Yemen", said the statement published by BNA.
Bahrain allies the United States and Britain have demanded Rajab's release and the dropping of cases against him.
In January, the activist was sentenced to six months in prison for insulting public institutions in his tweets.
He is awaiting the result of an appeal in that case, expected on May 4.
Rajab, who has led anti-government marches and heads the Bahrain Centre for Human Rights, was freed last May after serving two years in jail for taking part in unauthorised protests.
Bahrain, home to the US Navy's Fifth Fleet, has been rocked by unrest since security forces crushed Shiite-led protests in 2011 demanding a constitutional monarchy and an elected prime minister.