A U.S. Marine officer was acquitted by a military jury on Wednesday on charges he tried to cover up the shooting deaths of two dozen unarmed Iraqi men, women and children at Haditha in 2005.

In the first court-martial verdict from the high-profile case, Lt. Andrew Grayson was cleared at Camp Pendleton, California, after a five-day trial and less than half a day of deliberations by the jury.

Grayson, an intelligence officer, was not present when the 24 Iraqi civilians were shot to death near the scene of a roadside bombing at Haditha on November 19, 2005.

He was accused of ordering another Marine to delete photographs of the bodies from a computer and digital camera and lying to investigators.

The presiding judge, Maj. Brian Kasprzyk, dismissed an obstruction of justice charge against the 27-year-old native of Springboro, Ohio. Defence attorneys said in closing arguments that prosecutors bungled the investigation under intense media scrutiny.

Grayson, who served two tours of duty in Iraq, could have faced up to two decades in prison if convicted on all of the charges.

Two other Marines, including accused ringleader Staff Sgt. Frank Wuterich, still face courts-martial over the events at Haditha, which brought international condemnation.

Iraqi witnesses said angry Marines massacred unarmed civilians after a popular comrade, Lance Cpl. Miguel "TJ" Terrazas, was killed by a roadside bomb.

Defence attorneys said the civilians were killed during a pitched battle with insurgents in and around Haditha that followed the death of Terrazas.

Of the eight Marines originally charged by military authorities in December 2006, five have seen their cases dropped.

Wuterich's trial has been postponed until later this year pending an appeal of a discovery ruling. Lt. Col. Jeffrey Chessani is also awaiting trial.