BAGHDAD — Three explosions ripped through a public market on Thursday evening, killing at least 21 people and leaving a gruesome scene of scattered body parts and bloodied shoppers.

The attack, in a largely Shiite neighborhood, was notable in that it struck at civilians in the heavily fortified capital and left a high death toll. Many of the large-scale attacks lately have been against government institutions, like the police, as well as local officials.

Earlier in the day, an attack on an American convoy killed a civilian working for U.S.A.I.D. The victim, Dr. Stephen Everhart, was working with Baghdad University to develop a new business curriculum, according to a statement from the State Department.

One witness to the market attack, a dentist who owns a clinic nearby, described what he saw in the street after he heard two blasts.