An Israeli probe into its soldiers' deadly shooting of 15 emergency workers last month in Gaza says it has found evidence of "professional failures" and a deputy commander will be fired.

Israel at first claimed that the Palestinian medics' vehicles did not have emergency signals on when troops opened fire but later backtracked. Cellphone video recovered from one of the medics appeared to contradict Israel's initial account.

The military investigation, released Sunday, found that the deputy battalion commander, "due to poor night visibility," assessed that the ambulances belonged to Hamas militants. Video footage from the scene shows the ambulances had lights flashing and logos visible as they pulled up to help another ambulance that came under fire earlier.

The military said a preliminary inquiry indicated that "the troops opened fire due to a perceived threat following a previous encounter in the area, and that six of the individuals killed in the incident were identified as Hamas terrorists."

It did not provide evidence of how it determined that the six were Hamas militants, and the Islamist faction has rejected the accusation.

Eight Red Crescent personnel, six Civil Defence workers and a UN staffer were killed by the Israeli troops conducting operations in Tel al-Sultan, a district of the southern Gaza city of Rafah, before dawn on March 23.

Troops then bulldozed over the bodies along with their mangled vehicles, burying them in a mass grave. UN and rescue workers were only able to reach the site a week later to dig out the bodies.

The head of the Palestinian Red Crescent Society has said the slain men were "targeted at close range."

The Israeli military investigation said the Palestinians were killed due to an "operational misunderstanding" by Israeli forces, and that a separate incident 15 minutes later, when Israeli soldiers shot at a Palestinian UN vehicle, was a breach of orders.

No paramedic was armed and no weapons were found in any vehicle, Maj. Gen Yoav Har-Even, in charge of the military's investigative branch, told journalists.

The UN and Palestinian Red Crescent have demanded an independent inquiry.

The Israeli investigation found that the decision to crush the ambulances was wrong but denied that there was an attempt to conceal the event.

"The examination found no evidence to support claims of execution or that any of the deceased were bound before or after the shooting," it added.

A commanding officer is to be reprimanded for his "overall responsibility for the incident." A deputy commander dismissed for providing an "incomplete and inaccurate report" of the killings. It did not say if anyone would face criminal charges.

Israel has accused Hamas of moving and hiding its fighters inside ambulances and emergency vehicles, as well as in hospitals and other civilian infrastructure, arguing that justifies strikes on them. Medical personnel largely deny the accusations.