The first Palestinian Intifada (uprising) erupted in December 1987 and lasted until the Madrid Conference of 1991, despite Israeli attempts to suppress it. It was a partially spontaneous uprising, but by January 1988, it was already under the direction from the PLO headquarters in Tunis, which carried out ongoing terrorist attacks targeting Israeli civilians. The riots escalated daily throughout the territories and were especially severe in the Gaza Strip. The Intifada was renowned for its stone-throwing demonstrations by youth against the heavily armed Israeli Defense Forces. Over the course of the First Intifada, a total 1,551 Palestinians and 422 Israelis were killed. In 1987, Ahmed Yassin co-founded Hamas with Abdel Aziz al-Rantissi. Since then, Hamas has been involved in what it calls "armed resistance" against Israel, which includes mainly terrorist acts against Israeli civilian population.