At least 72 people were killed and about 130 wounded on Wednesday evening when a bomb exploded in the eastern Baghdad district of Sadr City, police and hospital officials said.

The explosion in the Shia area cast doubt on the readiness of Iraq’s security forces to keep a latent insurgency in check as US troops withdraw from the country’s cities. The blast, which occurred at the Mredi market, where birds are sold, happened shortly after sunset when it was crowded with shoppers who come out to make purchases after the summer’s scorching temperatures drop.