It is the fifth such detection in as many months and Israeli officials regard publicity around their tunnel hunts as a double-edged sword.
The number of protesters was smaller than in previous weeks, though still substantial and with Gaza's health ministry reporting dozens more Palestinians wounded by Israeli gunfire.
Palestinians killed in conflict with Israeli forces are often wrapped in their national or party flags, but there was something different about Yasser Murtaja's body ahead of his Saturday burial.
A Palestinian man was killed by Israeli gunfire in Gaza on Tuesday, Palestinian medics said, raising the death toll from clashes along the border to 17, and Israel's defence minister warned further protests would be met with similar force.
An Arab Israeli man was shot dead by soldiers on Tuesday after crashing into a hitch-hiking stop in the occupied West Bank and then attempting to flee, officials said.
Hamas, the dominant Palestinian group in Gaza, said five of the dead were members of its armed wing. Israel said eight of the 15 belonged to Hamas and two others came from other militant factions.
The Ministry of Foreign Affairs said in a statement that the Israeli escalation was a violation of international laws and conventions.
Tens of thousands of Palestinians, pressing for a right of return for refugees to what is now Israel, gathered at five locations along the fenced 65-km frontier.
Israeli occupation forces detained 13 Palestinians from different areas in the West Bank, including two youths with special needs.
Israel has warned that its soldiers could use live fire if Gaza Palestinians try to breach the border with Israel during a mass rally planned for Friday.
A senior Palestinian official on Friday slammed US President Donald Trump's choice of hardliner John Bolton as his new national security advisor.