BAGHDAD (AFP) - Two suicide bombings targeting Shi'ite pilgrims in Baghdad killed at least 11 people and wounded dozens more Thursday despite a heavy security deployment, Iraqi security and medical officials said.

The evening attacks struck in Mansur, west Baghdad, and Baab al-Sharji, in the centre, as worshippers prepared to commemorate the death of a revered figure in Shi'ite 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 attack in Baab al-Sharji killed three more, officials said.

The worshippers were walking to the northern neighbourhood of Kadhimiyah, site of a shrine dedicated to Imam Musa Kadhim, the seventh of 12 revered imams in Shi'ite Islam.

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

Shi'ite pilgrims are often targeted by Sunni militants who regard them as apostates, and in past years, multiple attacks have been carried out during the Imam Kadhim commemorations.

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.