A Hamas leader in the West Bank died in Israeli custody, Palestinian authorities and the group has said, AFP reports.

Mustafa Muhammad Abu Ara, 63, died after being moved from a prison in southern Israel to a hospital, according to a joint statement by the Palestinian Authority’s prisoners affairs body and the Palestinian Prisoners’ Club watchdog.

“We mourn the passing of the leader and prisoner Sheikh Mustafa Muhammad Abu Ara and hold the occupation responsible for his assassination through deliberate medical neglect,” Hamas said in a statement.

Abu Ara was arrested in October while suffering severe health problems, the Palestinian body and the watchdog said. During his detainment he was subjected to torture and starvation, they added.

Israel’s military did not immediately respond to a request for comment.