A third attack on an Iraqi police patrol in Baghdad killed two civilians, police said.
The violence came as Iraqi lawmakers prepared for a vote Wednesday on a security pact with the United States that would enable American forces to stay in Iraq for up to three more years under strict Iraqi oversight.
In the first attack, a bomb attached to a bus used by the Trade Ministry to ferry employees to work exploded shortly before 8 a.m. in eastern Baghdad, police and hospital officials said on condition of anonymity because they were not authorized to speak to the media.
Thirteen ministry employees were killed and three were wounded, according to an official with the state-owned Iraqi shopping centers company who also spoke on condition of anonymity. The company is part of the Trade Ministry.
The rush-hour attack occurred in a Shiite area and the injured were taken to Kindi hospital in Baghdad.
The U.S. military said 14 people were killed and four were injured in the 7:20 a.m. blast on the minibus. It said American soldiers assisted Iraqi police in securing the area and treating casualties.
About 45 minutes later, a female suicide bomber blew herself up as she stood in line to be searched at a checkpoint near the Green Zone in central Baghdad, killing seven people and wounding 13, according to an Interior Ministry official who declined to give his name.
The U.S. military said the bombing near the Green Zone occurred between 8:30 a.m. and 9 a.m. and killed two Iraqi army members and three civilians. One civilian was injured, it said.
The Green Zone houses the U.S. Embassy and the Iraqi government headquarters.
In a third attack, a roadside bomb targeted a police patrol around 10:30 a.m. near Technology University in eastern Baghdad, killing two civilians and wounding four other people, an Iraqi police officer and an official at Ibn al-Nafis hospital said on condition of anonymity. Two police officers were among the injured.
Meanwhile, the U.S. military is rushing to build criminal cases against some 5,000 detainees it deems dangerous - including suspected members of al Qaeda in Iraq - because the proposed security pact with Iraq would end its right to hold prisoners without charge.
The agreement, which is to be voted on by Iraqi lawmakers Wednesday, is primarily intended to set a timetable calling for American troops to leave Iraq by the end of 2011. But it also calls for control of security matters to shift to Iraqi authorities.
If passed, the deal would mean U.S. troops could no longer hold people without charge as they have since the 2003 invasion that ousted Saddam Hussein. Beginning Jan. 1, all detentions would have to be based on evidence, and the U.S. would have to prosecute prisoners in Iraqi courts or let them go.
"At the end of the day, if there's not enough facts to justify a court case, then we'll have to release," said Brig. Gen. David Quantock, the commander of the U.S. detention system in Iraq.
The Americans have evidence against only "a few hundred" of the most dangerous detainees, Quantock said, leaving open the possibility that thousands could find themselves back on Iraq's streets soon.
"We have a lot of work to do," he said.
Part of the challenge stems from differences between the U.S. and Iraqi legal systems. In the United States, forensic evidence is widely used in the courts. Not so in Iraq.