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.
The event marks the annual Palestinian Land Day, commemorating the killing of six unarmed Arab protesters in Israel in 1976.
It is expected to kick off more than six weeks of protests throughout the Palestinian territories leading up to the inauguration of the new US embassy in Jerusalem around May 14.
Gazans are expected to gather from Friday in camps being erected along the border fence, a few hundred metres from the Israeli lines.
Israeli armed forces chief Lieutenant General Gadi Eisenkot said in comments published Wednesday by local daily Yediot Aharonot that the current border tension presented the most serious risk of conflict since he took up his post in 2015.
Israeli tanks on Wednesday fired at positions of Gaza's Islamist rulers Hamas, in the wake of heavy gunfire from the strip, the detonation of roadside bombs aimed at Israeli border patrols and an incursion by three armed Palestinians who penetrated some 20 kilometres (12 miles) into Israel before being captured.
Eisenkot said reinforcements, including more than 100 special forces snipers, had been deployed to the border and the army was prepared for all scenarios.
Among them is the prospect of an attempt by protesters, organised or not, to break through the border fence which surrounds the Gaza Strip, home to two million Palestinians largely cut off from the rest of the world by Israeli and Egyptian blockades.
Officially, protest is being organised by civil society, but Israel believes that Hamas and allied groups are behind the plans.
The Israeli security cabinet was due to convene later Wednesday to discuss military preparations.
"We won't allow mass infiltration into Israel and to damage the fence," Eisenkot told Yediot.
"The instructions are to use a lot of force," he said. "In the event of mortal danger (to troops) there is authorisation to open fire."
- Women and children -
Soldiers posted at the border regularly fire live ammunition at Gazans who come too close, but Israel this time is worried about the possible presence of women and children in the danger zone.
Thousands, if not tens of thousands, of Gazans are expected to join border protests in coming six weeks, culminating on May 15 with a march toward the barrier.
That date is marked by Palestinians as the anniversary of the Nakba, or "catastrophe",when more than 700,000 Palestinians fled their land or were expelled during the war that led to the creation of Israel in 1948.
The United States plan to open its embassy around the same time, to coincide with the 70th anniversary of the foundation of the Israeli state, is further stoking palestinian anger.
The US decision to recognise Jerusalem as Israel's capital infuriated the Palestinians, who have broken off ties with the administration of President Donald Trump.
They claim the city's Israeli-annexed eastern sector as the capital of their future state, an aspiration which Trump did not address in his December declaration.
Hamas has said it would ensure that participants do not expose themselves to danger by going too close to approaching Israeli positions too closely.
But the latest border incidents have sent tensions soaring.
Hamas and Israel have fought three wars since 2008, the most recent of which in 2014 ended with a fragile truce.