(Adds updated information from the U.S. military)

May 23 (Reuters) - Nine U.S. soldiers were killed in five separate attacks across Iraq over the past 48 hours, most of them by roadside bombs, the U.S. military said on Wednesday.

The U.S. military had said in an earlier statement that the attacks had all taken place on Tuesday.

Here is a short chronology of the deadliest days for U.S. forces since the start of the war.

March 23, 2003 - The third day of the war - 28 U.S. soldiers are killed, mostly in fierce fighting in southern Iraq.

-- Nov. 2 - Chinook helicopter shot down near Falluja. Sixteen U.S. troops killed and 21 others on board hurt.

-- Nov. 15 - Two Black Hawk helicopters collide under fire in Mosul, 17 soldiers killed.

Jan. 8, 2004 - Black Hawk helicopter shot down near Falluja, killing all nine soldiers aboard.

-- April 29 - Car bomb near Mahmudiya, south of Baghdad, kills eight U.S. soldiers.

-- Dec. 21 - Suicide bomber in Iraqi uniform walks into mess tent at Mosul and kills 21 people, 18 of them Americans, including 14 U.S. troops.

Jan. 6, 2005 - Seven soldiers killed when a roadside bomb destroys their Bradley fighting vehicle in Baghdad.

-- Jan. 26 - U.S. Marine transport helicopter ferrying troops comes down in western desert, killing 31 aboard. Six more are killed in insurgent attacks.

-- June 23 - Seven troops, three of them women, killed in Falluja when a suicide car bomber detonates near a Marine truck.

-- July 24 - Four soldiers killed when a Humvee patrol vehicle is destroyed by a roadside bomb in Baghdad, and four killed when a Bradley fighting vehicle is hit by another bomb.

-- Aug. 3 - Fourteen Marines killed in a roadside bomb blast on a Marine amphibious assault vehicle near Haditha, northwest of Baghdad. A civilian interpreter was also killed.

-- Dec. 1 - Ten U.S. Marines are killed near Falluja in an insurgent bombing. Another is killed in Ramadi.

Jan. 5, 2006 - Eleven U.S. soldiers are killed in separate incidents, the worst of which was the deaths of five in Baghdad when a roadside bomb hit their patrol.

-- Jan. 7 - Eighteen U.S. soldiers are killed, 12 of whom died when a Blackhawk helicopter came down near the town of Tal Afar near Mosul, 390 km (240 miles) north of Baghdad.

-- Aug. 27 - Twelve U.S. soldiers killed in total in Iraq mostly in Baghdad.

-- Oct. 17 - Eleven U.S. soldiers killed in separate incidents all around Iraq.

-- Dec. 6 - Ten U.S. soldiers are killed in four incidents around Iraq, some killed by roadside bombs and others in combat.

Jan. 20, 2007 - A U.S. military helicopter goes down northeast of Baghdad, killing 12 people aboard. More soldiers are killed in clashes and roadside bombs. Twenty-five are killed in total.

-- Feb. 7 - All seven crew members and passengers aboard a U.S. Marine transport helicopter are killed after their aircraft crashed in Anbar province. Another four die in other incidents.

-- April 23 - Nine U.S. soldiers are killed at a military base north of Baghdad in Diyala province. 20 others are wounded.

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