Another 39 were wounded in the attack, which struck at 1:30 pm (1030 GMT) on the outskirts of the mostly Shiite town of Dujail in Salaheddin province. Among the dead and wounded were women and children.

"Nine people were killed and 39 wounded in the attack," said Salaheddin provincial spokesman Mohammed al-Aasi.

The pilgrims were walking to the city of Samarra to commemorate the death of the revered ninth century imam Hassan al-Askari at his gold-domed shrine in the majority-Sunni city. The commemoration falls this year on Saturday.

Dujail lies around 60 kilometres (40 miles) north of Baghdad in Saleheddin province, while Samarra lies 60 kilometres further north.

Tens of thousands of people died in violence sparked by the destruction of the Askari shrine's gold dome five years ago by suspected Sunni extremists loyal to Al-Qaeda.

The mosque itself was built in 944, and the golden dome was added in 1905.