Bahrain on Saturday extended by 15 days the period of detention for prominent rights campaigner Nabeel Rajab, who was arrested on April 2 accused of spreading false news.
A prosecution service statement said the Shiite militant was accused of "spreading tendentious rumours" about Bahrain's participation in the Saudi-led Arab coalition waging an air offensive against Shiite rebels in Yemen, as well as "attacking a state institution".
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 the official BNA news agency.
On Thursday, Bahrain allies the United States and Britain demanded Rajab's release and the dropping of cases against him.
On April 2, his family said Rajab was arrested for posting comments on Twitter denouncing alleged torture in a prison where Shiite activists are held.
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He said in a video posted on YouTube after his latest arrest that he was the victim of an "attempt by the authorities to deprive me of my right to free expression".
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, which is 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.
The Sunni Al-Khalifa dynasty rules the Shiite-majority Gulf kingdom with an iron fist.