Yasser Arafat Key adviser shot
Khalil al-Zebin, 59, a journalist and human rights activist, was gunned down outside his offices in the Palestinian controlled area.
It is thought he was shot several times shortly after midnight and died soon after being taken to hospital.
Palestinian police said they were investigating but no arrests had been made.
Zebin was a long-time Arafat loyalist whose monthly magazine focused on the rights of Palestinian prisoners held in Israeli jails.
Palestinian journalists have recently staged protests demanding that the Palestinian Authority investigate a recent series of attacks against them in the West Bank and Gaza Strip.
