Iraqi police and hospital officials say at least 50 people have been killed and more than 150 wounded in the Baghdad attacks.
They appear to have targeted Shi’ite neighborhoods.
A decade after the invasion that ousted Saddam Hussein, security remains fragile, although violence overall has dropped sharply over the years.
Many recent attacks have been claimed by Sunni militants linked to Al-Qaeda who want to destabilize the government.
Since late last year, thousands of Sunnis have been protesting against the Shi'ite-led government of Prime Minister Nuri al-Maliki, accusing his government of marginalizing Iraq's Sunni minority.
Meanwhile, U.S. President Barack Obama paid tribute to those who served in the Iraq War.
In a statement, Obama said the sacrifice of Americans gave the Iraqi people "an opportunity to forge their own future after many years of hardship."
He said the nation honors the memory of nearly 4,500 Americans who died in Iraq.