Gunmen travelling in three cars have opened fire in a Baghdad market, killing at least six pedestrians, police and medics say.
A string of suicide attacks, shootings and rocket strikes have claimed dozens of lives on a day of violence in Iraq.
At least 16 people were wounded when the drive-by shooting happened in the southern Zaafariniya area of the city.
In the bloodiest single incident, 13 Iraqi soldiers died when a suicide attacker drove a fuel tanker into an army base in Mosul in northern Iraq.
Earlier, a barrage of fire had hit the city's heavily fortified Green Zone.
Meanwhile, the US military said it killed 12 militants in a house east of Baquba, in Diyala province. It said they were preparing suicide attacks.
In further violence, at least 13 Iraqi soldiers were killed in a suicide bomb attack on an army base in the northern city of Mosul.
The bloodshed comes despite an overall reduction in violence since last June.
Mosul blast
That was when the US deployed an extra 30,000 troops in violence-hit areas - the so-called "troop surge".
The gunmen who mowed down shoppers in south Baghdad are reported to have fled the scene.
But Sunday's violence underlines the fragile, reversible nature of the apparent improvements in security, say correspondents.
Mosul has been a frontline of fighting in recent months
Huge blast
A medic at Ibn Nafis hospital confirmed receiving six bodies of people killed in the attack, reported AFP news agency.
At least 40 people were injured in Sunday's early-morning suicide strike in Mosul.
Elsewhere in Iraq, at about 0700 (0400 GMT), 13 soldiers died and about 30 people were injured in a huge blast in Mosul, caused by an explosives-laden tanker which ploughed into the army base.
Sunday also saw a barrage of fire hit Baghdad's Green Zone
Iraqi and US soldiers have been engaged in a major offensive in Mosul, the scene of intense insurgent activity in recent months.
The suicide attacker ploughed an explosives-laden tanker into the army base, causing a massive blast.
US commanders say Mosul is al-Qaeda's last urban stronghold in Iraq, and in January the Iraqi Prime Minister, Nouri Maliki, announced the start of a major counter-insurgent offensive.
Iraqi and US soldiers have been engaged in a major offensive in Mosul, which US commanders say is al-Qaeda's last urban stronghold in Iraq.
According to AFP, witnesses said Iraqi forces had sealed off the area around the base, in the Hermat neighbourhood of west Mosul.
In another deadly attack, at least seven shoppers in a Baghdad market were killed when gunmen travelling in three cars opened fire.
Military planes and helicopters were seen hovering above the base.
At least 16 people were wounded when the drive-by shooting happened in the southern Zaafariniya area of the city, police said. The gunmen fled the scene.
'Rogue elements'
In other violence:
at
least five people were killed by Katyusha rockets which apparently fell short of their target in Baghdad's heavily-fortified Green Zone
at
least five people were killed when a suicide bomber struck a queue outside a petrol station in the Shula district of Baghdad, police said
a
roadside bomb killed five Iraqi soldiers close to the city of Kirkuk - the scene of growing sectarian strife
Early on Sunday, a series of 10 or 12 rockets or mortars were fired into the Green Zone one - home of the Iraqi government HQ, the US and UK embassies, and thousands of American troops - at about 0600 (0300 GMT).
Bodies 'shaved'
As the barrage hit the Green Zone, the US public address system warned people "to duck and cover" and to stay away from windows.
The attacks on the Green Zone - which began at about 0600 (0300 GMT) and caused no reported injuries - set the warlike tone of the day.
The barrage of rocket or mortar fire sounded like successive peals of thunder in an audio recording of the attack.
The first rocket barrage sounded like successive peals of thunder. It left a shroud of stinking black smoke over the city, reports the BBC's Adam Brookes.
No casualties were reported in the attack, which left a shroud of stinking black smoke over the city, reports the BBC's Adam Brookes.
A second barrage followed about four hours later.
Previous rocket attacks on the Green Zone have been blamed on rogue elements of Moqtada Sadr's Mehdi Army militia.
Our correspondent says previous rocket attacks on the Green Zone have been blamed on rogue elements of Moqtada Sadr's Mehdi Army militia, which is supposed to be observing a ceasefire.
Moqtadr Sadr renewed a ceasefire for his militia last month.
Also on Sunday, the US military said it had killed 12 men in a raid east of Baquba city, in Diyala province.
Security in Iraq has improved overall since last June, when the US deployed an extra 30,000 troops in violence-hit areas.
Spokesman Major Winfield Danielson claimed six of the men killed were found to have shaved their bodies, which he said was "consistent with final preparation for suicide operations".
But our correspondent says the number of high-profile attacks has been creeping back upwards in recent months.
He added that a cache of weapons and ammunition had also been found in the raid and destroyed.
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