Palestinian medical officials say an Israeli airstrike killed a 12-year-old boy and a militant Sunday, bringing the death toll in Gaza since Friday to 17.

Israel is retaliating for more than 100 rocket attacks into Israeli territory in the worst flare-up of violence between Israelis and Palestinians in several years.

Thousands of Palestinian mourners took to the streets of Gaza Saturday for the funeral processions of those killed. Many of the marchers chanted “Revenge, revenge!”

Among the dead is Zuhair al-Qaissi, the leader of the Popular Resistance Committees . The group is best known for the 2006 abduction of Israeli soldier Gilad Schalit, who was freed last year in exchange for more than 1,000 Palestinian prisoners.

Israeli Defense Minister Ehud Barak said the air strikes will continue and the Israeli army will hit anyone planning to attack Israeli citizens.

“The whole round will continue as long as necessary to make sure that whoever has to be punished for these attempts to initiate terrorist attacks against Israeli as well as those who are trying to launch rockets at us will be punished.”

Israel said it launched the airstrikes because the PRC was planning an attack on Israel from Egypt.

A spokesman for Hamas – the Palestinian militants who rule the Gaza Strip – blames Israel for the violence.

“The Israeli occupation is completely responsible for this escalation and its consequences. The Hamas movement confirms the right of resistance of our people and the factions to defend themselves in facing these crimes.”

The escalating violence drew appeals for a cease-fire from the United States, United Nations and European Union.