The Palestinian Authority has criticised Israel's refusal to talk to more than 1,000 Palestinian detainees who are on hunger strike against conditions in Israeli jails.
Issa Qaraqe, head of detainees' affairs for the Palestinian Authority, warns of a "new intifada" if any of them die.
The strike is being led by Marwan Barghouti, a Palestinian leader jailed by Israel for life for five murders.
Israel had previously said there was "no reason" to negotiate with them.
Barghouti has been touted as a possible future successor to Palestinian Authority President Mahmoud Abbas.
He has been placed in solitary confinement for calling the strike, now in its third day.
Mr Qaraqe said 1,500 inmates had now joined the hunger strike. Israeli officials have not confirmed that number; the latest estimate by the country's prison service was that 1,187 detainees were involved.
There are fears that the hunger strike could fuel tensions across the Palestinian areas.
Mr Qaraqe warned that if prisoners die, "that could lead to a new intifada".
"If their demands are not met, more prisoners will join the strike," he was quoted by AFP news agency as saying.
"We have asked the international community and the UN to intervene immediately."
On Tuesday, Israeli Public Security Minister Gilad Erdan told Israeli public radio that Barghouti was "instigating mutiny and leading the hunger strike and that is a severe violation of the rules of the prison".
"They are terrorists and incarcerated murderers who are getting what they deserve."
The issue of Palestinians held in Israeli jails is an ongoing source of tension between the two sides.
Palestinians regard the detainees as political prisoners. Many have been convicted of attacks against Israelis.
Others are detained under so-called Administrative Detention, which allows suspects to be held without charge for six-month intervals.
There were about 7,000 Palestinians held in Israeli jails at the end of last year, according to Palestinian prisoners' groups.