BAGHDAD - Up to 50 people were killed and some 100 others wounded in a suicide bomb attack targeting Shiite pilgrims in Iraq's southern city of Basra on Saturday, a local police source said.

"The toll from suicide bomb attack against the pilgrims in Basra climbed to 50 killed and some 100 wounded, including women and children," the source told Xinhua on condition of anonymity.

The attack occurred at about 9:00 am local time (0600 GMT) when a suicide bomber blew himself up near a police checkpoint among a crowd of Shiite pilgrims marching to a shrine in the town of al-Zubair, south of the oil hub city of Basra, some 550 km south of Baghdad, the source said.

Iraqi security forces sealed off the scene as ambulances and civilian cars evacuated the victims to nearby hospitals and medical centers, the source added.

Earlier, the source said that 32 pilgrims were killed and some 100 others wounded by the blast.

Shiite pilgrims mark a major religious ritual of Arbaeen in their cities on Saturday, while hundreds of thousands of people march from different Iraqi cities towards the holy Shiite city of Karbala, some 110 km south of Baghdad, to commemorate the end of 40 days of mourning for Imam Hussein, Prophet Mohammad's grandson who was killed at the battle of Karbala in 680 AD.

Insurgents frequently attack Shiite pilgrims who perform communal rituals in Iraq, in attempts to provoke sectarian strife in the violence-shattered country.

Iraqi cities have been plagued by several attacks, including suicide bombings, since the US troops pulled out of the country earlier last month.