KABUL - More than 3,000 civilians were killed in the war in Afghanistan in 2011, the fifth year in a row the number has risen, the United Nations said on Saturday in a report likely to revive tension between the Afghan government and its Western backers.

Civilian deaths undermine support both in Afghanistan and the United States for the US-led war, and are one of the biggest causes of friction between President Hamid Karzai and the NATO-led International Security Assistance Force (ISAF).

Bombs planted on roads, and increasingly deadly suicide attacks that targeted civilians, killed more people than any other type of attack, according to the UN Assistance Mission in Afghanistan (UNAMA).

"The tactics of choice of anti-government elements subjected Afghan civilians to death and injury with increasingly lethal results in 2011," UNAMA said in a statement accompanying the report.

"Improvised explosive devices (IEDs) were the single largest killer of Afghan children, women and men in 2011."

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