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GAZA CITY - The terrible human toll from the nine-day Gaza conflict was laid bare Wednesday when four Palestinian boys from the same family were killed as they played football on a beach.

Three other children were wounded – one of them critically - in the attack, which appeared to be from Israeli naval shelling near the port area of Gaza City.

There were scenes of anguish at the nearby al-Shifa hospital as the parents of the victims learned of the attack. “My son! My son!” cried the mother of one of the boys.

The attack - and its heartrending aftermath – was witnessed by NBC News. Moments earlier, the boys were playing soccer with journalists on the beach.

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The four victims were named as Ahed Atef Bakr and Zakaria Ahed Bakr, both 10 years old, Mohamed Ramez Bakr, 11, and Ismael Mohamed Bakr, 9.

Moutaz Bakr, 1 of the boys who survived #Israeli shelling, was shaking w a broken army, blood shot eyes, says he saw 3 of his friends killed - Ayman Mohyeldin (@AymanM) July 16, 2014

Zakaria’s father rushed to the hospital after hearing of the attack only to learn that his son had been killed. “He was my only son ... he died with his cousins, they all died together,” he told NBC News.

“We live by the coast. There was a headline on the news that four children were injured ... so we went looking for the kids and we could not find them, so we came here to the hospital to look for them and we found them all, including my son ... oh my God.”

Ashraf al-Qidra, spokesman for the Gaza Health Ministry, said: "This is a cowardly crime.”

"When the first shell hit the land, they ran away but another shell hit them all," said Abu Hassera, 22, whose shirt was stained with blood. "It looked as if the shells were chasing them," he told Reuters.

Israel’s military has warned tens of thousands of Palestinians to leave their homes as the conflict escalates, raising fears that a full ground invasion of Gaza is imminent. However, many do not heed the warnings because Hamas dismisses them as psychological propaganda – and because it is not immediately clear where Palestinians are supposed to go while the entire Gaza Strip is under threat of Israeli airstrikes.

A #Palestinian mother reacts to the news that her son was one of 4 boys killed in Israeli shelling of #gaza seaport pic.twitter.com/2LdGY5p9GU - Ayman Mohyeldin (@AymanM) July 16, 2014

The Gaza beach area has been shelled frequently since Israel began its offensive in the enclave on July 8 following a surge in Palestinian cross-border rocket strikes.

Wednesday's strikes brought the Palestinian death toll in the nine-day conflict to 213 – including 43 children – with 1,600 wounded, according to Hamas.

On the Israeli side, one man was killed Tuesday and several people were wounded - the first death in the Jewish state since the fighting erupted on July 8. The Israeli victim, Dror Hanin - who was killed by a mortar shell near the Erez crossing - was expected to be buried later Wednesday.

Hamas officially told Egypt Wednesday that it has rejected the proposed truce, but Tuesday’s volley of rockets into southern Israel had already dashed hopes of a cease-fire.

Alastair Jamieson and Alexander Smith contributed to this story from London, Yael Factor from Tel Aviv