A pickup truck parked in a market for spare car parts exploded in the Amil district in western Baghdad on Tuesday afternoon, killing 17 people and wounding 55 others, police said.
The blast damaged 10 nearby houses and a Shiite mosque and set eight cars ablaze, police said.
"A truck was driving from here and heading towards the mosque. When I saw it I shouted "a car bomb, a car bomb" and people started to run and took shelter in that house," one man said at the scene.
An hour earlier a parked minibus packed with explosives blew up in an area filled with bus stops and shops in Tayaran Square, central Baghdad, killing 23 people and injuring 68 others, police said.
Also on Tuesday eight U.S. soldiers were killed in roadside bombings and a helicopter crash in the restive Diyala province north of Baghdad, the military reported, making May the deadliest month of the year for U.S. troops in Iraq.
Three German citizens working for a German computer company were kidnapped from an Iraqi Finance Ministry office in Baghdad, an Iraqi government official said, and two car bombings killed 40 people in the capital, police said.
And in Samarra, 95 kilometres (60 miles) north of Baghdad, set up fake checkpoints on the outskirts of the city and abducted more than 40 people, most of them soldiers, police officers and members of two tribes that had banded together against local insurgents, police said.
The violence and kidnappings came a day after U.S. and Iranian officials met in Baghdad under the auspices of Iraqi Prime Minister Nouri al-Maliki to try to end it.