The attack happened on Thursday in the town of Tuz Khurmatu, about 200km north of Baghdad, as visitors flocked to the shrine of Ahmad ibn Musa al-Kadhim, the son of one of the 12 religious leaders whom Shia consider imams.
Police Colonel Abd Allah Hasan al-Bayati said that the dead were an Iraqi soldier, a civilian and a five-year-old child, and that half of the wounded were civilians.
A spokesman for Salahddin governorate, where Tuz is, said three people were killed and 14 wounded.
The shrine is revered by the town's Kurdish and Turkmen Shia populations.
The area that includes the oil-rich city of Kirkuk is the scene of frequent violence between the Kurds on one hand and the Turkmen and Arabs on the other.
Ukrainian to pull out by October
Ukrainian President Viktor Yushchenko confirmed Thursday that Kiev would withdraw its last remaining troops from Iraq next October, as tentatively planned, Interfax news agency reported.
"It will be mid-October," Yushchenko told a news conference in Kiev.
He added that the exact date for the withdrawal could still change.
"Our conceptual position is the following: Our troops must leave Iraq this year," Yushchenko said.
A first batch of 137 soldiers returned home earlier this month, and in May, Ukraine plans to cut the now 1300-strong force to some 850.
Also on Thursday, Iraqi journalist Khalid Abd Allah, speaking to Aljazeera from Samarra, said armed men attacked the headquarters of al-Imam police station in the city's centre.
In the exchange of fire that followed, one of the fighters was killed, he said.
Abd Allah quoted a police officer as saying later that the dead man was an Arab but not an Iraqi and that a car bomb had exploded in al-Dhubat, also in the central part of Samarra.
The car bomb targeted a patrol as well police personnel and left seven people dead, including three civilians, and 15 civilians wounded, Abd Allah said.
A visit to Samarra general hospital revealed that three civilians had died and 15 others had been wounded, seven of them seriously, Abd Allah reported.
Iraq's Shia, who have been the target of some of the deadliest attacks since the fall of Saddam Hussein's government, observed Arbain on Thursday, the end of a 40-day mourning period for the killing of revered Imam Husain almost 14 centuries ago.
The largest gathering will be in Karbala, south of Baghdad, where Husain is believed to be buried.
Devastating bombings in Karbala and at Baghdad's Kadhimiyah shrine one year ago killed 180 people.
In a separate explosion also on Thursday, Aljazeera learned three Iraqi police officers were injured when a bomb targeting a police patrol exploded in the central Iraqi southern city of Basra.
The blast damaged a police vehicle and another car.