By Emma Farge

GENEVA (Reuters) -The head of the Palestinian Red Crescent said on Thursday that a paramedic who survived an attack that killed 15 aid workers was spared because he asked Israeli soldiers for mercy in Hebrew, adding that he hoped the man's testimony would help win justice.

Assad Al-Nassasrah, a Red Crescent paramedic, survived shootings that killed 15 emergency and aid workers on March 23 in southern Gaza in an incident that drew international condemnation. Their bodies were found buried in a shallow grave a week later by Red Crescent and U.N. officials who accused Israeli forces of killing them.

Al-Nassasrah went missing and then was freed from Israeli detention on April 29 and has not yet publicly commented. One other paramedic survived.

Younis Al-Khatib, president of the Palestine Red Crescent Society, told reporters in Geneva that Al-Nassasrah was spared after he pleaded in Hebrew and said his mother was a Palestinian citizen of Israel.

"What does Assad say in Hebrew? 'Don't shoot. I am Israeli.' And the soldier got a bit confused," he told reporters. "That confusion ... made him survive."

"Assad will be a witness that can put all the Israeli stories in shambles," he added.

Israel's prime minister's office and its diplomatic mission in Geneva did not immediately respond to a request for comment.

The Israeli military initially said its soldiers had opened fire on vehicles that approached their position "suspiciously" in the dark without lights or markings. It said they killed six militants from Hamas and Islamic Jihad who were travelling in Red Crescent vehicles.

But video recovered from the mobile phone of one of the dead men and published by the PRCS showed emergency workers in their uniforms and clearly marked ambulances and fire trucks, with their lights on, being fired on by soldiers.

On April 20, the Israeli military said a review into the incident had found there had been "several professional failures". It said a deputy commander, a reservist who was the field commander, would be dismissed.

The military advocate general is conducting its own investigation and criminal charges could be pursued, according to the military.

Asked how Al-Nassasrah was treated in custody, Al-Khatib said: "like a Palestinian". He said Al-Nassasrah had been interrogated and that he had mental health issues, but did not elaborate further.

Social media footage shared by the Palestinian Red Crescent dated the day after his release showed Al-Nassasrah crying as he hugged medics and looking dazed while being examined in a Gaza hospital. Eight of those killed were from the PRCS, which provides medical aid in Gaza and is part of the world's largest humanitarian network.

Al-Khatib said the organisation was working with lawyers and considering formal submissions to international courts and to the U.N. Security Council.

"We think the international community is responsible to provide justice to those killed," he said. "We don't train our people to go and die."

(Reporting by Emma Farge, Editing by Rosalba O'Brien)