"Reports of explosive experts and forensic evidence at the crime scene showed that a suicide terrorist wearing an explosive belt caused the explosion, during which 30 citizens were killed and more than 50 others wounded," the media office of the Joint Operation Command said in a brief statement.
The intelligence service is gathering information to hunt down the terrorist group responsible for the attack and bring them to justice, the statement added.
Earlier, a source with the Iraqi interior ministry told Xinhua that a bomb detonated at a crowded market in Sadr City, a suburb district of Baghdad, targeting people shopping for the Eid al-Adha, a grand Muslim festival that coincides with the annual Hajj in Saudi Arabia.
Meanwhile, the extremist Islamic State (IS) militant group claimed the attack and said its suicide bomber named Abu Hamza al-Iraqi blew himself up among a crowd of Shiite people, the IS said in a brief statement, the authenticity of which could not be independently verified.
Deadly bombings have been rare in Baghdad, as the security situation has improved in Iraq since Iraqi security forces fully defeated the IS militants across the country late in 2017.
However, IS remnants have since melted into urban areas or deserts and rugged areas, carrying out frequent guerilla attacks against security forces and civilians.