The death toll of a bomb explosion at a crowd of Shiite pilgrims in the holy city of Karbala on Wednesday rose to 20 and 117 people were wounded, an Interior Ministry source said.

"The latest reports said that 20 Shiite pilgrims were killed and 117 others were wounded by the massive bombing in Karbala," the source told Xinhua on condition of anonymity.

A suicide bomber driving a minibus struck crowds of Shiite pilgrims gathering near the Technical Institute on the eastern entrance of Karbala, some 110 km southwest of Baghdad, for major religious ritual, the source said.

Earlier, the source said that the massive blast was carried out by a bomb planted on a cart pulled by a motorcycle, putting the toll at 10 killed and 85 others wounded.

The attack targeted Shiite pilgrims who were marching from the southern Iraqi provinces to Karbala to observe the Friday Arbaeen ritual (40 days after the day of Ashura), the source added.

Tens of thousands of pilgrims gather at major Shiite commemorations which have been frequently targeted by deadly attacks carried out by various armed groups in Iraq, mainly, to incite sectarian violence in the war-torn country.

Despite relative drop of violence, attacks are still common in Iraq as part of recent deterioration in security which shaped a setback to the efforts of the Iraqi government to restore normalcy in the country just a few weeks before the March general elections.