Five people were killed and 17 others wounded on Monday in a suicide bomb attack targeting Shiite pilgrims in northern Iraqi capital Baghdad, an interior ministry source said.A suicide bomber wearing an explosive vest detonated himself among a crowd of Shiite pilgrims at a security checkpoint in Shaab district in Baghdad, the source told Xinhua on condition of anonymity.The pilgrims were heading to the holy Shiite city of Karbala, south of Baghdad, to observe the Arbaeen religious ritual ahead of its climax day next on Thursday.Arbaeen is the 40th day after the martyrdom anniversary of Imam Hussein, Prophet Muhammad's grandson and the third holy figure for the Shiite Muslim sect, who was killed in the battle of Karbala in 680 AD.Insurgents frequently attacked Shiite pilgrims who perform communal rituals in the Iraqi cities, killing and wounding hundreds of them in attempts to provoke sectarian strife in the violence-shattered country.