Six US soldiers were killed today in two separate roadside bomb attacks on patrols in Iraq, the military said in statements.
Four were killed in the area of the town of Yusufiya, just south of Baghdad; it was one of the heaviest single US losses for some time.
A statement gave no further details.
Two others died shortly after 9am (6am Irish time) near Balad, 60 km (40 miles) north of the capital, a second statement said.
Since early this year, US commanders have been concerned about the increasing use of more powerful or more sophisticated improvised bombs capable of penetrating armoured vehicles and inflicting much heavier casualties in each attack.
The southern fringes of the capital, sometimes referred to as the Triangle of Death, have seen considerable violence by Sunni Arab insurgents against neighbouring Shi'ite residents and US forces defending the Shi'ite-led government.