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A Palestinian man runs with a white flag in the Shuja'iyya neighbourhood, which was heavily shelled by Israel during fighting, in Gaza City July 20, 2014. reuters/Finbarr O'Reilly

In what was the bloodiest day of fighting in the two-week old Operation Protective Edge, more than 100 Palestinians and 13 Israeli soldiers were killed in Gaza on Sunday, taking the overall death toll to 500, Al Jazeera reported Monday.

The Shuja’iyya district reportedly witnessed the maximum number of civilian casualties on Sunday -- with over 60 deaths -- as Israel escalated its military onslaught in the region.

“Dozens of civilians, including children, have been killed in Israeli military strikes in the Shuja’iyya neighborhood in Gaza,” U.N. Secretary-General Ban Ki-moon said, on Sunday. “I condemn this atrocious action. Israel must exercise maximum restraint and do far more to protect civilians.”

Ban, who is in Doha on the first leg of a Middle East tour met Qatar's Emir Sheikh Tamim bin Hamad al-Thani, Palestinian President Mahmoud Abbas and Qatari Foreign Minister Khaled al-Attiya on Sunday in an attempt to broker a truce between Hamas and Israel. The U.N. Security Council is scheduled to hold an emergency meeting, convened by Jordan, on the conflict in Gaza on Monday.

According to a Guardian report, Palestinian President Mahmoud Abbas described the bloodshed in Shuja'iyya as a "heinous massacre" and called on the international community to intervene immediately to stop the "Israeli aggression.”

Nabil el-Araby, head of the Arab League, also described the shelling on Gaza as "a war crime against Palestinian civilians."

Israeli President Benjamin Netanyahu, meanwhile, said that the operation in Gaza would continue “as long as is needed,” Jerusalem Post reported Sunday.

Netanyahu reportedly also said that Israel is speaking to various entities in the region, including the Palestinian Authority, but Hamas did not want to be a “part of a peace process” and was responsible for the large number of deaths in Gaza.

Meanwhile, human rights groups in Gaza accused the Israel Defense Forces, or IDF, of using flechette shells, which spray out thousands of tiny and potentially lethal metal darts, as part of its military operation in Gaza, according to the Guardian.

B'Tselem, an Israeli human rights organization told the Guardian that such a weapon, while not against international humanitarian law, was “likely to result in civilian injuries.” The IDF did not deny using the shells in the conflict, stating that it was only using weapons “determined lawful under international law.”