The head of Bahrain Centre for Human Rights is to remain in jail, despite being granted bail by a Bahrain court in Manama.
Nabeel Rajab, arrested earlier this month on his on arrival at Manama airport from Lebanon, was granted bail on Sunday in the case of "insulting an official authority".
His charges centered on four messages posted on the social media site Twitter that suggested the interior ministry had not carried out proper investigations into civilian deaths.
"The judge agreed to the request to free him on $800 bail with a travel ban, but he has not been released because he is being detained on another charge," said Mohamed al-Jishi, Rajab's lawyer.
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The second charge against Rajab, of organising illegal demonstrations, could land the activist in jail for two years, al-Jishi said last week.
Witnesses and the prosecution said that the new hearing for Rajab, will convene on Tuesday, the AFP news agency reported.
Rajab led many protests that were part of the ongoing uprising led by the Shia Muslim majority against the Sunni ruling al-Khalifa dynasty that rules the island.
Bahrain has rejected calls for an elected government and large-scale protests which began in February 2011 after successful revolts in Egypt and Tunisia, continue weekly in Shia villages, often resulting in clashes with police.
Authorities have vowed to "get tougher" on security. Activists have said that the government wants to find any way of keeping Rajab off the streets.
'Deplorable' rights record
New York-based advocacy group Human Rights Watch (HRW) has called for the United Nations to scrutinise what it called Bahrain's "deplorable" rights record when the UN Human Rights Council conducts its Universal Periodic Review of the country on Monday.
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"The international community should push Bahrain to adopt specific measures to ensure free expression and peaceful assembly, end torture, free political prisoners, and establish credible accountability mechanisms for continuing abuses," HRW said in a statement on Sunday.
Abdulhadi Abdulla Alkhawaja, another human rights activist and seven other activists were sentenced to life in prison by a military court last year for participating in the protests. Alkhawaja has been on a hunger strike for more than 100 days.
Thirteen men jailed for leading last year's protests remain in jail after a military court convicted them last year, despite revelations, in a report by a human rights commission in November, of systematic use of torture to extract confessions.
Official figures show 35 people had died by the time a period of martial law ended in June but opposition activists say the number has risen to 81 as police try to limit protests.
The government rejects the figure, saying many fatalities were due to tear gas exposure by people with prior health conditions.
Activists say five people have died in suspicious circumstances this year, including a 23-year-old man who prosecutors say drowned. An independent autopsy later provided information that suggested he was likely tortured with electricity before drowning.