The UN Security Council condemned the violence after an emergency session.
UN deputy political affairs chief Taye-Brook Zerihoun told the council the situation in Gaza "might deteriorate in the coming days" and called for civilians, particularly children, not to be targeted, Reuters news agency reports.
"Israel must uphold its responsibilities under international human rights and humanitarian law," he said.
In a written statement before the meeting, Israel's ambassador to the UN, Danny Danon, blamed the bloodshed on Hamas - the militant group that controls the Gaza Strip, a Palestinian territory.
The UN envoy for Palestine Riyad Mansour told the council that more than 1,400 Palestinian civilians had been injured.
Palestinian President Mahmoud Abbas said the Israeli authorities bore "full responsibility" for Friday's deaths.
Thousands of Palestinians marched to the border at the start of a six-week protest, dubbed the Great March of Return.
Israel's military, which oversees a no-go zone along the Gaza border, doubled its troop presence for the protest
Palestinian medical officials say at least sixteen Palestinians have lost their lives and more than a thousand others sustained injuries when Israeli military forces opened fire on thousands of protesters, who have flocked to a sit-in near the border fence between the Gaza Strip and occupied Palestinian territories.
Friday was the single deadliest day in the Israel-Palestine conflict since the 2014 Gaza war.
