United Nations chief Ban Ki-moon raised deep concern on Tuesday over Palestinian hunger strikers in Israeli prisons, saying they must be charged and tried or be released.
Ban highlighted the case of Samer Issawi, who has been refusing food since August 1 and is in a "critical health condition."
"The secretary general is deeply concerned over the rapidly deteriorating condition of Palestinian prisoners in Israeli custody who are on hunger strike," said UN spokesman Martin Nesirky, singling out Issawi's case.
Palestinian President Mahmud Abbas and Arab League secretary general Nabil al-Arabi have both written to Ban about Issawi and three other long term hunger strikers.
Ban raised the cases during recent talks with Israel's Prime Minister Benjamin Netanyahu, said Nesirky.
"Of particular concern are the detainees held in administrative detention without charges," said the spokesman.
"Those detained should be charged and face trial with judicial guarantees in accordance with international standards, or be promptly released," he added.
"The secretary general urges for a solution to be reached without delay in order to resolve the prisoners' plight and preserve calm."
A Jerusalem court on Tuesday refused bail for Issawi. He is likely to be indicted at a new hearing on Thursday, his lawyer said.
Issawi was released from Israeli detention under a prisoner swap deal in October 2011, but was rearrested in July following allegations that he violated the agreement by going to the West Bank.
Palestinian prisoners on a previous long-running hunger strike agreed to end their protest in May last year when Israel agreed to improve conditions.
Ban's spokesman stressed the importance of keeping to the accord, including by respecting family visiting rights.
"International human rights obligations towards all Palestinian detainees and prisoners under Israeli custody must be fully respected," he said.