BAGHDAD, Iraq (AP) - A suicide bomber driving a truck loaded with a ton of explosives hidden beneath cooking oil, canned food and bags of flour obliterated a Baghdad food market on Saturday, killing at least 121 people in one of the most fearsome attacks in the capital since the U.S. invasion in 2003.

It was the fifth major bombing in less than a month targeting predominantly Shiite districts in Baghdad and one provincial city to the south. This one leveled about 30 shops and 40 houses, witnesses said.

The Health Ministry said more than 300 people were injured in the thunderous explosion that sent a column of smoke into the sky on the east bank of the Tigris River. The nearby al-Kindi hospital - quickly overwhelmed - began turning away the wounded and directing ambulances to hospitals in the Shiite Sadr City neighborhood.

U.S. Ambassador Zalmay Khalilzad said the bombing was