BAGHDAD, Feb 15 (Reuters) - Four U.S. soldiers were killed by roadside explosions during combat operations in Iraq's Diyala province on Wednesday, the U.S. military said. Three soldiers died when bombs exploded near their vehicles northeast of Baghdad. A fourth died later of his wounds in hospital. Two other soldiers were wounded in the attack, a U.S. military statement said on Thursday. The deaths came as U.S. and Iraqi forces set up checkpoints and stepped up patrols in Baghdad on Wednesday as a long-promised offensive against militants got under way.
