Israeli troops fired warning shots toward Palestinian youths gathered at the Gaza-Israel border on Saturday, wounding 13 people, health officials said.

Tension remained high in the area a day after deadly violence broke out in one of the biggest Palestinian demonstrations there in years.

An Israeli military spokesperson said he was checking the details of Saturday’s unrest.

On Friday at least 15 Palestinians were killed by Israeli security forces confronting protesters, some of whom the military said had opened fire, rolled burning tires and hurled rocks and fire bombs toward troops across the border.

Palestinian President Mahmoud Abbas declared Saturday a national day of mourning and a general strike was called across the occupied West Bank. Thousands in Gaza marched through the streets at funerals for those killed.

Tens of thousands of Palestinians had gathered on Friday along the fenced 65-km frontier, where tents were erected for a planned six-week protest pressing for a right of return for refugees and their descendents to what is now Israel. The Israeli military estimate was 30,000.

Families brought their children to the encampments just a few hundred meters (yards) from the Israeli security barrier with the Islamist Hamas-run enclave.

But hundreds of Palestinian youths ignored calls from the organisers and the Israeli military to stay away from the frontier and violence broke out.

Palestinians marking 'catatstrophe'

The protest, organised by Hamas and other Palestinian factions, is scheduled to culminate on May 15, the day Palestinians commemorate what they call the “Nakba” or “Catastrophe” when hundreds of thousands fled or were driven out of their homes in 1948, when the state of Israel was created.

Israel has long ruled out any right of return, fearing an influx of Arabs that would wipe out its Jewish majority. It argues that refugees should resettle in a future state the Palestinians seek in the Israeli-occupied West Bank and Gaza. Peace talks to that end have been frozen since 2014.

Israel withdrew its troops and settlers from Gaza in 2005 but still maintains tight control of its land and sea borders.

Egypt also keeps its border with Gaza largely closed.

- Reuters