An Israeli airstrike on the Gaza border killed a Palestinian man on Thursday morning, the health ministry in the enclave said.
The unidentified man died in Shifa Hospital in Gaza city after being targeted by an Israeli strike near the border, as tensions increased ahead of new protests expected on Friday.
The Israeli army said an aircraft had "targeted an armed terrorist adjacent to the security fence".
It said it would "not allow any harm to the security of Israeli civilians." It did not specify if the strike was carried out by a drone or other aircraft.
Also, a Palestinian wounded in the mass protest along the border last week died of his wounds on Thursday, bringing the death toll to 20.
Eighteen Palestinians had already been killed by Israeli forces when Friday's protests led to violence.
The march was mobilised by Hamas and was the first in six weeks of protests set to culminate on May 15, the day after the anniversary of the official establishment of Israel and 70 years since Nakba - the displacement of 700,000 Palestinians
On Thursday a prominent campaign by an Israeli rights group urged soldiers to refuse to shoot at unarmed Palestinians.
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The campaign by the B'Tselem NGO, which included advertisements in Israeli newspapers, led Israel's public security minister to suggest the group should be investigated for calling for sedition.
"Soldier, rules of engagement that can cause the death of civilians who do not pose a danger to human lives are illegal," the NGO said.
Israel has pledged to stop attempts to damage the heavily fortified fence on the Gaza border and to prevent illegal infiltrations, including with live fire if necessary.
Public Security Minister Gilad Erdan told Israel's army radio on Thursday that he had asked the attorney general to examine whether B'Tselem should be investigated for "calling for sedition."
"Concerning rules of engagement, soldiers treat any activity putting Israel's security in danger as terrorist acts," he said.
Israel's use of live fire last week has come under criticism from rights groups, while the European Union and UN chief Antonio Guterres have called for an independent investigation.
Gaza's ruling Hamas group have offered to pay $3,000 (Dh11,000) to the family of any Palestinian killed by Israeli troops along the border.
In a statement, the group said it would support the "family of each martyr" with $3,000, while those seriously wounded would receive $500.
The payments were being provided "in light of the difficult economic conditions experienced by our people in the Gaza Strip as a result of the continued Israeli siege".