Israel responsible for Palestinian prisoner death: PLO
The Amman-based Palestinian National Council (PNC) -- the legislative body of the PLO -- called for an investigation into the Israeli medical negligence and crimes against Palestinian prisoners.
"This crime is added to the series of Israeli crimes against Palestinian prisoners in Israeli jails, due to deliberate medical negligence," the PNC said in a statement.
Demanding an investigation into the death of al-Sayeh, the PNC called on international legal and human rights organizations, in particular the International Committee of the Red Cross, to investigate alleged Israeli medical negligence crimes against Palestinians prisoners.
It also called for pressuring Israel to fulfill its responsibilities and obligations to international laws on the protection of prisoners.
The legislative body claimed that 6,000 Palestinian prisoners were currently languished in Israeli jails.
In Ramallah, several Palestinian groups organized a sit-in, displaying al-Sayeh's photos. They condemned Israeli treatment of Palestinian prisoners.
Reports said al-Sayeh had suffered from bone and blood cancer since 2011. He was arrested in 2015, accused of killing an Israeli officer in the West Bank.
According to the Palestinian Authority, as many as 220 Palestinians have lost their lives inside Israeli jails, many due to medical negligence.