(Adds quote, new details, other violence) BAGHDAD, May 22 (Reuters) - Thirty-two people were killed in three attacks on Shi'ite Muslim pilgrims walking in Baghdad on Thursday evening ahead of a major religious holiday, police and medical sources said. The attackers defied a shutdown of major roadways for Shi'ite religious faithful, who were heading to the Imam Kadhim shrine in Kadhimiya in western Baghdad to commemorate the death of the Shi'ite saint in 799. The deadliest was in eastern Baghdad, near Tayaran Square, where a minibus approached a crowd of pilgrims and exploded, killing 14 people and wounding 17 others, according to police and medical sources. Across Baghdad, in the western neighbourhood of Mansour, a parked car exploded, killing six people and wounding 38.