There are growing fears for the life of Abdulhadi al-Khawaja, the jailed Bahraini human rights leader who has been on hunger strike for 78 days, as his family say they have been unable to contact him since Monday.
His death would lead to an explosion of rage from Bahrain's Shia majority who have been demanding political and civil rights from the Sunni al-Khalifa monarchy. Tension is already high after the death a week ago of a protest leader, Sala Abbas Habib.
"No one has been able to see him since 1pm on Monday," said Jim Loughran, spokesman for the Front Line Defenders, a human rights group formerly headed by Mr Khawaja. He said Mr Khawaja, who is held in the hospital of the Bahrain Defence Force, had previously been in touch daily with members of his family or his lawyer. The only government statement on his health was on Twitter from the Interior Ministry, saying he was "in high spirits".
Mr Khawaja has reportedly been refusing water and fluids since 21 April. One explanation for his silence might be that the authorities are force feeding him. He has said he will fast until death unless he is freed after being sentenced to life imprisonment by a military court for trying to overthrow the government last year.
His daughter, Zainab, has also been detained for seven days after she was arrested during protests. The staging of the Formula One Grand Prix a week ago and Mr Khawaja's hunger strike have led to an escalation in protests.
Demonstrators threw petrol bombs at a police station as thousands of mourners visited the grave of Mr Habib on Thursday. The Interior Ministry said it is investigating how he died.