The Israeli authorities should immediately release a Palestinian detainee or charge her with a recognizable criminal offence and promptly try her, Amnesty International said amid fears that the woman could die in detention after 37 days on hunger strike.
Hana Shalabi, 30, from the village of Burqin in the northern West Bank, is allegedly affiliated with the Islamic Jihad movement but has never been charged with a criminal offence.
She was transferred to Meir Hospital in the central Israeli town of Kfar Saba on Tuesday night, but remains under Israeli custody and constant armed guard.
"When her lawyers and independent physicians have been given access to her, Hana Shalabi has reported that Israel Prison Service officers have handled her violently while transferring her to hospital or the military court, and consistently pressured her to end her hunger strike," said Ann Harrison, Amnesty International's deputy director for the Middle East and North Africa.
"Amnesty International has repeatedly called on the Israeli authorities to release Hana Shalabi and other Palestinians held in administrative detention, unless they are promptly charged with internationally recognizable criminal offences and tried in accordance with international fair trial standards."
Under administrative detention, Israeli military orders allow the authorities to detain Palestinians from the occupied West Bank without trial indefinitely if they are deemed to be a "security threat".
Hana Shalabi began her hunger strike in protest against ill-treatment during her arrest on 16 February, and continued in protest against her detention without charge or trial after receiving an administrative detention order five days later.
A doctor from Physicians for Human Rights - Israel (PHR) who saw her on Monday reported that she was at risk of death because she could suffer from heart failure at any moment, and called for her immediate hospitalization.
According to PHR, she has lost 14kg (31lbs) since her arrest, and suffers from impaired thyroid functions and severe pain, weakness and dizziness.
"If she remains in detention, she - and all other Palestinian detainees who have joined her hunger strike in protest against the policy of administrative detention - must be treated humanely at all times and receive regular access to medical treatment by an independent physician in a setting that respects the privacy of the doctor and patient, " said Ann Harrison.
A military judge has yet to rule on the appeal against her four-month detention order, even though the Military Court of Appeals held its first hearing more than two weeks ago on 7 March.
Hana Shalabi was one of 1,027 Palestinian prisoners and detainees freed from Israeli jails as part of a deal to free captured Israeli soldier Gilad Shalit in October and December last year. Before she was re-arrested in February, she had planned to study nursing at al-Rawda College in Nablus.
Prior to her release in October 2011, she was held for 25 months without charge or trial in HaSharon prison, under administrative detention orders that were repeatedly renewed.
There are also reports that the Israeli authorities may be considering force-feeding her, which could constitute cruel and inhuman treatment. As a general rule, hunger strikers should not be forcibly fed.
Her family has yet to receive permits to visit despite repeated requests by international and local organizations. They have not seen her since her arrest on 16 February.
More than 20 other Palestinian detainees and prisoners held in several Israeli prisons have declared open-ended hunger strikes against the policy of administrative detention, some for more than three weeks.
To Amnesty International's knowledge, they have not been allowed access to independent doctors, and some may also have been denied access to lawyers, isolated, or punished in other ways following their decisions to go on hunger strike.
"No detainees should be punished in any way for their decision to go on hunger strike. The Israeli authorities must ensure that all detainees on hunger strike are treated humanely and allowed access to lawyers and independent medical professionals," said Ann Harrison.
More than 300 Palestinians, including more than 20 members of the Palestinian Legislative Council, are currently being held in administrative detention.