On Saturday, Vermont Senator Bernie Sanders criticized Israel's use of force at the Israel-Gaza Friday after clashes between Palestinian protesters and Israeli soldiers left 15 dead and over 700 wounded by live fire.

"The killing of Palestinian demonstrators by Israeli forces in Gaza is tragic," said Sanders. "It is the right of all people to protest for a better future without a violent response."

"Meanwhile," he added in a post to Twitter, "the situation in Gaza remains a humanitarian disaster. The U.S. must play a more positive role in ending the Gaza blockade and helping Palestinians and Israelis build a future that works for all."

Friday's demonstrations in Gaza and the West Bank kicked off the "March of Return," a series of mass protests marking Palestinian Land Day slated to continue for weeks.

Israel has since said that 10 of those killed were active members of Hamas' armed wing and two other militant groups, while Hamas has acknowledged that five of the dead were members of its armed wing.