Israeli troops shot dead three protesters along the Gaza border on Friday, Gaza medics said, hours after the United Nations human rights chief criticized Israel for using "excessive force" against demonstrators.

Israeli troops have killed 41 Palestinians and wounded more than 5,000 others since Gaza residents began staging protests along the border fence on March 30 to demand the right of return for Palestinian refugees.

The troops were holed up behind fortifications on their side of the 40-km (25-mile) border fence and fired live ammunition and tear gas at protesters at five locations on the Gazan side.