Article published on the 2009-02-13 Latest update 2009-02-13 17:04 TU
Sixty-five people were injured in the attack, according to the Interior Ministry.
The bomber had hidden her explosives under an abaya, the traditional Muslim head-to-toe black garment for women, said Captain Mohammed al-Awadi of the Babil province police.
This is the deadliest attack since a woman suicide bomber killed 35 peoiple near a Shia shrine in Baghdad on 4 January.
Earlier this month police announced that they had arrested a woman who confessed to recruiting more than 80 volunteers for suicide missions agains Shia-Muslims and helped orchestrate dozens of attacks.
Karbala provincial governor Akeel al-Khazali told reporters Friday that five million pilgrims, including 110,000 from abroad, have already arrived in the city.
Arbaeen marks the passage of 40 days since the Ashura festival, which commemorates the killing of the prophet Mohamed's grandson, Hussein, in a battle which established the split between Sunni and Shia Muslims.
Friday's attack came a day after eight pilgrims were killed and more than 50 wounded in a bombing near Karbala's revered Imam Hussein shrine.