The other explosion took place nearly simultaneously across town at a crowded bus stop where passengers were lining up to catch rides to eastern Shiite neighborhoods, though police said the target was the passing convoy of a top Iraqi police general.
Three people were killed and 15 wounded, Brig. Nazar Majeed among them, said an officer on condition of anonymity because he was not authorized to talk to media.
The small zone includes shops that sell spare auto parts and tires, and is frequently used as a shortcut for Interior Ministry convoys trying to avoid traffic jams on another main street leading to government buildings, the officer said.
Tareq Salman, who owns a tea stall nearby, said he heard a huge explosion and then saw smoke spewing from the bus station.
"I saw several passengers running and several minibuses on fire. I saw wounded men screaming for help and police cars taking some seriously wounded to the hospital," 54-year-old Salman said. "There were blood stains and one burned body."
"Most of my tea cups were broken and some car parts shops were damaged," he said.
Such blasts - once a somber but daily feature of life in Iraq's capital - have become far less frequent since a U.S. troop buildup last year. A truck loaded with rockets exploded Wednesday in northeast Baghdad, killing 18 people in the deadliest single blast in more than two months.
Meanwhile, the U.S. military said it killed four suspected militants, captured five others and destroyed two safehouses Saturday in northern Iraq.
American soldiers called in airstrikes and killed the four men after coming under small-arms fire southwest of Mosul, a military statement said. They also destroyed two buildings filled with weapons, ammunition and graffiti indicating they were used for foreign militants, it said.
Five men were captured Saturday in a separate raid in Mosul, including two accused of conspiring with senior al-Qaida in Iraq leaders in the city, the military said.
Mosul is believed to be one of the last urban strongholds of the terror group, and U.S. and Iraqi forces have fought fierce battles against militants there in recent months.