Iraqi officials say a relentless wave of bombings has rumbled across Baghdad and nearby towns, killing at least 56 people and wounding more than 200.

The more than a dozen attacks Tuesday - mostly car bombings - highlight increasing sectarian tensions in Iraq a decade after the war began.

The attacks came on the eve of the anniversary of the U.S.-led invasion, which started before dawn on March 20, 2003.

One of the deadliest of the attacks hit near a main gate to the heavily-fortified Green Zone, which houses major government offices and the embassies of several countries, including the United States and Britain.

Police and hospital officials provided the casualty toll. All officials spoke on condition of anonymity because they aren't authorized to talk to the media.