BAGHDAD - At least ten people were killed and more than 21 others wounded in a suicide bomb attack targeting Shiite pilgrims in the Iraqi capital of Baghdad on Thursday, police said.

The attack occurred around noon when a suicide bomber blew up his explosive vest among a procession of Shiite pilgrims walking on a highway in Doura district in the southern part of Baghdad, the source told Xinhua on condition of anonymity.

The pilgrims were heading to the holy Shiite city of Karbala, some 110 km south of Baghdad, to observe the Arbaeen religious ritual ahead of its climax day next Tuesday.

The casualty toll could rise as ambulances and police vehicles transferred the wounded to different hospitals and medical centers in Baghdad, the source said, adding that some wounded were in critical condition. ?

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 A.D.

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.

Many Iraqis are worried about a resurgence of violence, ethnic and sectarian strife that nearly tore the country apart few years ago.

Iraq is witnessing its worst violence in recent years. According to the UN Assistance Mission for Iraq, 8,109 Iraqis were killed in the country from January to November this year.