Car bombs have rocked the Iraqi city of Ramadi, killing 20 people, the latest in a string of attacks during the day that have caused dozens of casualties.
The US is defending the idea behind its controversial wall
Three cars exploded in quick succession near a restaurant and market in the western district of al-Taamim.
Witnesses said there was a heavy police presence in Ramadi because of reports that there were explosives there.
Earlier blasts hit Baqouba and Mosul, and near where the new US envoy was giving his first briefing in Baghdad.
Ambassador Ryan Croker said the next few months were critical in the effort to reconcile Iraq's warring communities and urged the government to make use of a US-led security plan in the capital.
He also defended the thinking behind a controversial wall being built around the flashpoint Adhamiya area, a Sunni enclave on the mainly Shia east bank of the Tigris.
On Sunday Iraqi Prime Minister Nouri Maliki said he had ordered a halt to the project after it drew strong criticism from residents and Sunni leaders.
Earlier in the day, at least 10 people died in Tal Uskuf, just north of Mosul, when a suicide bomber detonated his car outside an office of the Kurdistan Democratic Party.
An eyewitness in the mainly Christian town said residents were in deep shock as it was the first time it had been hit in the four years of Iraq's insurgency.
Police said a suicide car bomber struck a police station in Baqouba, north-east of Baghdad, killing at least 10 people.
And in the Iraqi capital itself, at least seven people died in a suicide attack in Karradat Mariam, metres from the edge of the Green Zone where Mr Crocker was delivering his briefing.
Another car bomb exploded close to the Iranian embassy in Baghdad. One person was reported killed in the blast, in a car park used by people visiting the Iranian mission.
More than 150 people were reported wounded in the succession of blasts.