The Palestine Red Crescent Society on Monday gave new details of the Israeli attack on its paramedics and other emergency responders in the Gaza Strip that killed at least 15 people last month, saying Israeli forces had targeted them in a “series of deliberate attacks.”

Speaking at a news conference in the West Bank, Red Crescent officials said Israeli troops shot at the rescue workers in waves over a two-hour period before dawn on March 23. They termed the killings “a full-fledged war crime” and called on the United Nations Security Council and the international community to demand accountability and an independent investigation.

The Israeli military, which has admitted to killing the 15 men, said on Monday that a “preliminary inquiry indicated that the troops opened fire due to a perceived threat following a previous encounter in the area,” and it would continue investigating. It said that six of those killed “were identified as Hamas terrorists,” but cited no evidence.

The Red Crescent and the United Nations have said that the dead were unarmed aid workers who posed no threat. They said the men were wearing their uniforms and riding in clearly marked emergency vehicles, flashing their emergency lights.