WORLD BRIEFING

An improvised bomb killed two U.S. service members in southern Afghanistan, where U.S. and NATO troops have stepped up their operations against insurgents in recent months, NATO said.

Also in the south, a British soldier was killed in an attack on a foot patrol, and another NATO service member died in a blast, NATO and British officials said.

Taliban militants this year have increased their use of roadside bombs, which now account for the majority of U.S. and NATO casualties. Fighting has been particularly harsh this summer in the south.

The U.S. and North Atlantic Treaty Organization have a record number of troops in Afghanistan -- nearly 100,000 in total -- and the top commander in Afghanistan, Army Gen. Stanley McChrystal, is likely to soon request thousands more.