April 8 (Reuters) - The U.S. Congress on Tuesday and Wednesday is receiving reports on the state of war in Iraq from the U.S. commander on the ground, Gen. David Petraeus, and Washington's ambassador to Baghdad, Ryan Crocker.

Tens of thousands of civilians have been killed in sectarian violence which gripped Iraq since the U.S.-led invasion in 2003. Here are some details on casualties in Iraq.

* IRAQI CIVILIANS:

-- The latest tolls from the widely cited human-rights group Iraq Body Count (IBC) show that up to some 90,200 civilians have been killed since 2003. Of those, some 22,586 to 24,159 civilian deaths were recorded in 2007 through the Web site's own monitoring of media and official reports.

-- With two exceptions (May and July 2007), the 2007 civilian death toll in Baghdad fell steadily month on month, according to Iraq Body Count. By December 2007 this had fallen to 246, about one-seventh of the starting January total of 1,683.

-- In contrast, the monthly toll outside Baghdad increased substantially between January (1,112) and August (1,604), before a steep drop to around 700 per month and below for September through December, its figures show.

-- Despite a sharp rise in February 2008, the figure of 633 killed was still dramatically lower than the 1,645 civilians who died violently in the same month the previous year.

* U.S. MILITARY:

-- U.S. military deaths have reached 4,020 since the invasion in 2003, IBC figures show.

-- According to icasualties.org, an independent Web site that tracks military deaths, there was a steady decline in the second half of 2007. Nevertheless 2007 was the deadliest year for U.S. troops in Iraq with 901 killed, underscoring a new counter-insurgency strategy of moving troops off large, relatively safe bases and into small neighborhood garrisons.

Sources: Reuters/ www.icasualties.org *

/www.iraqbodycount.net **

NOTES:

* = www.icasualties.org uses official information from Centcom or the Department of Defense. The U.S-led military coalition toll includes casualties from Iraq and the surrounding area where troops are stationed.

** = www.iraqbodycount.net (IBC), run by academics and peace activists, based on reports from media sources. The IBC says on its Web site the figure underestimates the true number of casualties. (Writing by David Cutler and Paul Grant)

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