A militant umbrella group that includes al-Qaeda in Iraq says it was behind the wave of bombings in Baghdad on Tuesday which killed more than 50 people.
The Islamic State of Iraq described the violence as "the first drop of rain", after which it would have its "revenge" for those executed by the authorities.
On Monday, the justice minister said "nothing" would halt the executions of militants guilty of capital offences.
The bombings also came on the 10th anniversary of the US-led invasion.
Although violence has decreased in Iraq since the peak of the insurgency in 2006 and 2007, attacks are still common and at least 220 civilians were killed in February.
At least 50 people died and 160 others were wounded in the co-ordinated wave of suicide, car and roadside bombings in and around Baghdad during Tuesday's morning rush hour.
The assailants targeted markets, restaurants, bus stops and day labourers mainly in Shia districts of the capital, although two of the deadliest blasts occurred near the heavily-fortified Green Zone and the offices of the ministry of labour and social affairs.
On Wednesday morning, a statement posted on jihadist websites by the Islamic State of Iraq claimed the attacks had been a "quick response" to the justice minister.
"What has reached you on Tuesday is just the first drop of rain, and a first phase, for by God's will, after this we will have our revenge," the statement added.
Iraq put at least 129 people to death last year and carried out several mass executions, including one in which 21 people were killed in a single day, according to the AFP news agency.
The BBC's Jim Muir in Baghdad says Tuesday's bomb attacks both reflected and aggravated the profound crisis currently afflicting Iraqi politics.
Prime Minister Nouri Maliki accused those behind the attacks of trying to provoke a sectarian civil war. He said regional intelligence services were involved, in an effort to destabilise the country.
The government also announced that provincial elections, scheduled for 20 April, would be delayed in the troubled, mainly Sunni provinces of al-Anbar and Nineveh, where sentiment against Mr Maliki is strong.
But, our correspondent says, it is not just the Sunnis who are at odds with him.
The Kurds have already withdrawn their government ministers from Baghdad.
And now, from within Mr Maliki's own Shia community, the militant cleric Moqtada Sadr has told the five ministers loyal to him to boycott cabinet meetings and threatened to pull out of the government and parliament, our correspondent adds.