JERUSALEM — A Palestinian militant held by Israel marked 44 days on hunger strike on Monday, with a rights group saying his life was in danger but prison authorities describing his condition as satisfactory.

Tel Aviv-based Physicians for Human Rights said in a statement that 34-year-old Khader Adnan, arrested by Israeli troops on December 17 and held without trial in what Israel calls "administrative detention", began a hunger strike the following day in protest at his imprisonment.

"His health is deteriorating and his life will be in danger if he continues the hunger strike," the group said in a statement after its doctors examined him. "He does not eat and only drinks water."

The Palestinian prisoners' club, which monitors inmates' wellbeing, said that Adnan was taken by ambulance on Monday from Israel's Ramla prison to a military court, where a hearing on his case was postponed until February 1.

Israel Prison Service spokeswoman Sivan Weizman told AFP that Adnan's condition was being closely monitored by prison doctors.

"If necessary he will be taken to a hospital for further treatment," she said. "All the effects of hunger-striking have been explained to him... We shall consider forced feeding if it becomes necessary."

She said that Adnan, a member of Islamic Jihad, started his fast in protest at his imprisonment.

Weizman said the adjournment in Monday's court hearing was at his lawyers' request.

"According to (medical) examinations his condition is satisfactory," she said. "Considering the length of time he has been on hunger strike it's satisfactory."