A Palestinian prisoner's health is "rapidly deteriorating" as he enters the 12th day of his hunger strike, according to his father.

Hassan Showka, from the occupied West Bank city of Bethlehem, was arrested on September 29 without charges for a second consecutive time. He is being held in administrative detention at Israel's Ofer prison.

"He does not have family visitation rights, so we can't see him, but we're in touch with his lawyer, who is able to see him every now and then," his father, 57-year-old Hassanein Showka, told Al Jazeera.

{articleGUID}

Hassan, 29, has been denied the right to see his family members, including his toddler.

Administrative detention is a legal procedure that allows Israel to imprison Palestinians from the occupied West Bank and the Gaza Strip without charge or trial, for renewable periods of up to six months. Israeli authorities have been using this procedure for more than 50 years, based on secret evidence.

"The lawyers who manage to see him [Hassan] depict to us his current state, but most times we're unsure whether the picture depicted is 100 percent accurate - usually they want to spare us the pain," Hassanein said.

"They don't want us to worry about him, but we know he's unwell."

Earlier this year, Hassan went on another hunger strike to protest his previous term of administrative detention, his father said. He was arrested again days later.

Today, there are some 600 administrative detainees in Israeli prisons, 16 of whom are children.

"Administrative detention is a real problem. We've been trying to understand why, what's the purpose behind his arrest, but we're still left wondering and haven't been provided with a valid explanation," Hassanein said. "From the day they took him and until this very moment, we're all confused … This is our son and he's precious to us."

Hunger strikes have traditionally been used as a way to pressure Israel into improving living conditions in prisons and to push for basic rights, including visitations.

Deprivation of rights

On Monday, Mousa Soufan, a prisoner diagnosed with advanced lung cancer, was planning to start an open-ended hunger strike to protest medical neglect in Israeli prisons, local media reported.

Under international law, Israel is obliged to maintain the wellbeing of the prisoners in its custody.

Amina al-Taweel, a spokesperson for the Hebron-based Palestinian Prisoners Center for Studies, told Al Jazeera that those in administrative detention are treated the same as prisoners facing charges.

"The rights they're deprived of, including healthcare, visitation rights and their overall living conditions are identical to those prisoners who actually face charges," Taweel said. "But those who are on hunger strike specifically face very dangerous consequences."

{articleGUID}

Earlier this year, 1,500 Palestinian prisoners embarked on a 40-day hunger strike to achieve better conditions.

It was dubbed as the longest hunger strike in the history of the prisoners' movement. They survived on salt and water, and eventually managed to gain more visitation rights and access to phone booths.

Addameer, a Ramallah-based prisoners' rights group, told Al Jazeera that the conditions in Ofer prison - which mostly holds administrative detainees - are dire, with overcrowded cells that often hold up to six people at a time.

There are also "insect and rat infestations", said Dawoud Yusef, Addameer's advocacy coordinator.

"Collective punishment is common, where the Israeli prison service imposes price surges at the canteen, strips prisoners of their bi-monthly visits, and withholds medical treatment," he said. "Solitary confinement is common … They are locked within the cell for 23 hours a day, mostly without sunlight, and are often shackled during their one hour outside."

This year, the number of arrests surged for the first time in years. Throughout the summer months, more than 1,000 Palestinians were arrested in the aftermath of the al-Aqsa crisis in occupied East Jerusalem, which erupted in July after three Palestinian citizens of Israel killed two Israeli guards. The attackers were also shot dead.