Clashes erupted as tens of thousands of Gazans marched near the Israeli border in a major protest on Friday, leaving at least 15 Palestinians dead and hundreds more wounded in one of the worst days of violence in recent years.

Late in the day, Israel's military targeted three Hamas sites in the Gaza Strip with tank fire and an air strike after what it said was an attempted shooting attack against soldiers along the border that caused no injuries.

Protesters, including women and children, had earlier gathered at multiple sites throughout the blockaded territory, which is flanked by Israel along its eastern and northern borders.

Smaller numbers approached within a few hundred metres of the heavily fortified border fence, with Israeli troops using tear gas and live fire to force them back.

Israeli security forces also used a drone to fire tear gas toward those along the border from overhead in one of the first uses of the device, a police spokesman said.

The health ministry in Gaza reported 12 Palestinians killed by Israeli forces throughout the day. More than 1,200 were wounded by various means including tear gas, it said.

Palestinians accused Israel of using disproportionate force, as did Turkey.

Israel's military alleged that the main protests were being used as cover by militants to either break through the border or carry out attacks.

“It is not a peaceful demonstration,” an Israeli military official told journalists.

“There was no small number of attempts to damage the fence and cross” the border, she added. The army said it estimated some 30,000 demonstrators were taking part in the protests.

It said that “rioters are rolling burning tyres and hurling firebombs and rocks at the security fence and at (Israeli) troops, who are responding with riot dispersal means and firing towards main instigators.”

Playing with your life

Protesters were demanding hundreds of thousands of Palestinian refugees who fled or were expelled during the war surrounding Israel's creation in 1948 be allowed to return.

Hamas leader Ismail Haniya attended the protest, believed to be the first time he had gone so close to the border in years. Far smaller protests broke out in parts of the occupied West Bank.

On Friday evening, Gazan leaders called on protesters to retreat from the border area until Saturday, with the demonstration planned to extend six weeks, until the inauguration of the new US embassy in Jerusalem around May 14.

Palestinian president Mahmud Abbas also declared Saturday a day of national mourning. The upcoming embassy move has added to tensions surrounding the march.

US President Donald Trump's recognition of Jerusalem as Israel's capital in December has infuriated Palestinians, who claim its annexed eastern sector as the capital of their future state.

The protest also began as Jewish Israelis prepared to mark the Passover holiday, which began on Friday evening.

Israel announced a “closed military zone in the area surrounding the Gaza Strip,” accusing its Islamist rulers Hamas of using the lives of civilians “for the purpose of terror”.

It deployed reinforcements, including more than 100 special forces snipers, for fear of mass attempts to break through the security fence.

Israeli Defence Minister Avigdor Lieberman said in a Twitter post directed to Gazans in both Hebrew and Arabic that “Hamas's leadership is playing with your life”.

Hamas has fought three wars with Israel since 2008.