The evening attacks struck in Mansur, west Baghdad, and Baab al-Sharji, in the center, as worshippers prepared to commemorate the martyrdom of a revered figure in Shiite Islam.

The bombing in Mansur killed eight people and wounded 26 others, according to a police colonel and a medical source.

The attacker was dressed in an all-black women's robe, or abaya, apparently to avoid attention, according to the capital's security spokesman, Brigadier General Saad Maan.

Another suicide attacker detonated a car bomb in Baab al-Sharji, central Baghdad, killing three more, while a vehicle rigged with explosives in the northern neighbourhood of Urr left five dead.

The worshippers were walking to the northern neighborhood of Kadhimiyah, site of a shrine dedicated to Imam Musa Kadhim (PBUH), the seventh of 12 revered imams in Shiite Islam.

The two-day rituals marking the anniversary of his martyrdom in 799 AD are due to climax on Saturday and Sunday.

Shiite pilgrims are often targeted by foreign backed takfiri militants.

Due to the heightened threat of attack, the authorities have imposed heavy security measures on the capital, involving the closure of entire roads and barring certain vehicles from the streets.

NJF/NJF