Israel´s military said Tuesday it had closed its investigation into the 2009 killing of at least 21 Palestinian civilians in a Gaza air strike after deciding not to charge those involved.

In a written response to a query by AFP, the army spokesman´s office said allegations of war crimes against military personnel had proved to be unfounded.

"The Military Advocate General, Brigadier General Dani Efroni, has stated his opinion regarding alleged... war crimes in Gaza´s (Zeitun) neighbourhood," it said. "According to the findings, the investigation found the accusations groundless."

"The Military Advocate General also found that none of the involved soldiers or officers acted in a negligent manner," it continued. "In conclusion... Efroni decided that legal action should not be taken, and ordered for the investigation to be terminated immediately."

A statement from the Israeli rights group which had filed a complaint into the strike on a Gaza home during the Operation Cast Lead offensive against Palestinian militants said it was "unacceptable that no one is found responsible for an action of the army that led to the killing of 21 uninvolved civilians."

"The military´s response does not detail the findings of the investigation, nor does it provide the reasons behind the decision to close the file or any new information about the circumstances," the group, B´Tselem, added.

Gaza´s ruling Hamas movement said that the military´s decision made the original killing of the family worse still.

"This is a worsening of the crime and an attempt to evade legal and international prosecution," Hamas spokesman Fawzi Barhoum told AFP. A UN commission investigating the 22-day Israeli offensive on Gaza put the toll of members of the Al-Samouni family killed in the strike at 29.

Its chairman, South African judge Richard Goldstone, said it was one of the most serious incidents his team investigated.

He has said that Israel´s inquiry into the attack found it was apparently due to a commander´s misinterpretation of a drone image. "Israel´s closure of the Samouni file is like encouraging the killing of more of our people," Barhoum said.

The military said on Tuesday that Efroni had forwarded recommendations to the military high command, "to ensure that such events will not happen again. These recommendations are to be implemented immediately."

Cast Lead, launched on December 27, 2008, cost the lives of 1,400 Palestinians -- at least half of them civilians -- and 13 Israelis, including 10 soldiers. (Copyright © 2012 Agence France Presse. 05/01/12)