Palestinian stone-throwers clashed on Friday with Israeli troops in several locations along the Israel-Gaza border fence, as mass sit-ins touted by Gaza's Hamas rulers as peaceful protests, quickly spun out of control.

Two Gazans were shot dead by Israeli forces in clashes, the Palestinian health ministry said, bringing to four the number of people killed during a day of border protests. Israeli troops fired live bullets and tear gas at Palestinians on the other side of the border fence. The Palestinian Health Ministry said at least 15 people were wounded by army fire.

The sit-ins are seen as a new attempt by Hamas to break a crippling, decade-old Gaza border blockade by Israel and Egypt that has made it increasingly difficult for the group to govern. Friday's actions are to be the first in a series of protests planned in Gaza in the coming weeks. The activities are to culminate on May 15, the 70th anniversary of Israel's creation, with a march through the border fence.

Palestinians commemorate the date as the anniversary of their mass displacement and uprooting during the 1948 Mideast war over Israel's creation. The vast majority of Gaza residents are descendants of Palestinians who fled or were driven from communities in what is now Israel.