Khalil al-Hayya, a senior Hamas official, suggested on Monday that armed groups in the Gaza Strip could take action against Israel in the coming days, hours after Israeli security forces killed dozens of Palestinians in the border region between Israel and the coastal enclave.Tens of thousands of Palestinians participated in a major protest in multiple places in the border region on Monday.Since March 30, many Palestinians have participated in protests in the border region, especially on Fridays, to support the return of Palestinian refugees and their descendants to their former and ancestral homes in Israel and pressure Israel to lighten its restrictions on the movement of goods and people in and out of Gaza.The IDF described the protest on Monday as a “violent riot,” asserting that protesters lobbed firebombs and rocks at its forces, attempted to place an explosive device near the border fence between Israel and Gaza and tried to pass into the Jewish state's territory.In leaflets the army dropped in Gaza on Monday morning, it also warned protesters not to approach the border fence.However, international and local human-rights groups accused the army on Monday of using “excessive force” against “unarmed protesters.” Fifty-eight Palestinians were killed and 2,771 were wounded in the protest, according to Ashraf al-Qidra, a spokesman for the Hamas-run Health Ministry in Gaza.“Our people’s peaceful and popular march has tempted the enemy to kill more of us and spill more of our blood. Therefore, we clearly state today… that the patience of resistance factions, including first and foremost Hamas and the Kassam Brigades, will not last for a long time,” he said at a press conference in the border region, alluding to Hamas’s armed wing, Izzadin Kassam.The last major conflict between Israel and armed groups in Gaza took place in 2014 when the two sides fought against each other in a war that lasted more than 50 days.At a meeting of the Ramallah-based Palestinian leadership, Palestinian Authority President Mahmoud Abbas accused Israel of carrying out “a massacre” in Gaza and said flags will be flown at half staff for three days and that a strike will be observed on Tuesday.He did not say if the strike will include schools and health institutions.Abbas also slammed the US for opening the US Embassy in Jerusalem on Monday, referring to the diplomatic office as a “settlement outpost.”“We heard that the [Americans] opened an embassy,” he said. “It is not an embassy. It is an American settlement outpost.”Many Palestinians and Palestinian officials have been furious since US President Donald Trump announced his intention to open a US embassy in Jerusalem in December. The Palestinian leadership has long hoped to build the capital of a future Palestinian state in east Jerusalem and called for the final status of Jerusalem to be settled in negotiations between itself and Israel.Jordanian Foreign Minister Ayman al-Safadi condemned Israel on Monday for its use of force against the protesters in Gaza.“Israel killing of 28 Palestinians [in] Gaza is a crime that’ll only produce violence. Excessive use of force against Palestinians exercising right to protests occupation won’t ensure security,” he said in the afternoon.The Egyptian Foreign Ministry also sharply criticized Israel on Monday: “Egypt rejects the use of force against peaceful marches demanding legitimate and just rights, and warns of the negative consequences of this dangerous escalation in the occupied Palestinian territories.”In his comments at the press conference, Hayya also said the protests in the border region will continue.On Tuesday, Palestinians are slated to mark what they call the “Nakba,” which refers to the displacement of hundreds of thousands of Palestinians in the conflict surrounding the creation of Israel in 1948.Another major protest in the border region is slated to take place on Tuesday.