Four U.S. soldiers died Sunday night in a roadside bombing in Iraq, bringing the American toll in the five-year war to 4,000.

The four were killed when a homemade bomb hit their vehicle as they patrolled a southern Baghdad neighborhood, the U.S. military said Monday.

A fifth soldier was wounded.

The grim milestone comes less than a week after the fifth anniversary of the U.S-led invasion of Iraq.

Of the 4,000 U.S. military personnel killed in the conflict, 3,263 have died in combat and attacks, and 737 in non-hostile incidents, such as traffic accidents and suicides.

Eight of the killed were civilians working for the Pentagon.

Also Sunday, at least 35 Iraqis died in suicide bombings, mortar fire and when gunmen in cars opened fire in a crowded outdoor market.

Nearly 100 were wounded in the violence.

Estimates of the Iraqi death toll since the war began range from about 80,000 to hundreds of thousands.

Another 2 million Iraqis have been forced to leave the country, and 2.5 million have been displaced from their homes within Iraq, according to the U.N. High Commissioner for Refugees.

Nearly 160,000 U.S. troops remain in Iraq, continuing to wage a war that has cost U.S. taxpayers about 500 billion U.S. dollars.

Editor: Yan