A Palestinian family who lost contact with their son after a quick evacuation from their Gaza City home found him killed in a shocking video posted online.

In footage filmed by a Palestinian TV crew and released by the International Solidarity Movement, Salem Khaleel Shamaly searches through the rubble created by Israeli air strikes in hope of finding his family in the Shejaiyah neighbourhood.

He is then shot in the hand by an assailant thought to be an Israeli sniper and, while he is lying on the ground amid the rubble, two more shots ring out, leaving Shamaly motionless.

A sister and a cousin of the missing 23-year-old, who both fled the Shejaiya neighbourhood, watched the video in horror as they heard Shamaly's voice.

Muhammad Abdellah, from the International Solidarity Movement, said: "Israeli soldier sniper hit him in his hip, so he laid down. And I started to ask him 'can you move?' But he said 'no, I cannot move, my blood is going everywhere'.''

"I guess it was in his heart or almost there, because he was dying in front of our eyes."

Despite activists witnessing Shamaly's death, his body was abandoned as shelling continued, forcing the search party to retreat.

His cousin, Mohammed Alqattawi, said that after watching the video he and his uncle were now seeking help to find and retrieve the young man's body.

The footage was shot in the Shejaiya neighbourhood - where at least 60 Palestinians and 17 IDF soldiers were killed on Sunday - during a two-hour humanitarian ceasefire between Israel and Hamas militants.

The footage does not offer conclusive evidence on the identity of the killer due to the distance from which the shots were fired and the close proximity of the search party filming the incident to Shamaly.

At least 649 Palestinians and 31 Israelis have now been killed in Israel's ground and air offensive on the Gaza Strip, which sought to prevent Hamas rocket fire.