A female suicide bomber killed 32 people and wounded 84 others south of Baghdad on Friday when she blew herself up on a major Shi'ite religious pilgrimage route, police said.

The attack in Iskandariya, 40 km (25 miles) south of the capital, came a day after a bomb killed eight people in the Shi'ite holy city of Kerbala, to which hundreds of thousands of pilgrims were headed to commemorate Arbain.

The Arbain rite is one of the most important events in the Shi'ite religious calendar, and marks the end of a mourning period after the anniversary of the death in the seventh century of the Prophet Mohammad's grandson Imam Hussein.

Some pilgrims said the bomb attacks would not deter them.

"We came here for the pilgrimage. Nothing will stop us. We aren't afraid. We've been through worse events in the past," said 63-year-old Sadia Ali, who had travelled to Kerbala from Baghdad's Sadr City slum.

The attacks occurred despite heavy security on the pilgrimage route.

The Arbain rite, which culminates early Monday morning, is difficult to secure. Many pilgrims walk all the way to Kerbala, and are easy targets as they cover hundreds of km (miles) clutching religious banners.

Emergency services have been on high alert, and the public was asked to give blood in case of attacks.

"We have been on alert since last Saturday. From then till now I haven't been able to take even an hour to go and see my family. I have been sleeping in the ambulance," said emergency worker Ahmed Kadhom.

Kadhom said that after Thursday's attack, he saw a grief-stricken man carrying his dead young son.

"He was shouting and crying. I will never forget this scene," he said.

Sunni Islamist insurgents such as al Qaeda have often attacked large Shi'ite religious gatherings during the years of sectarian slaughter that followed the 2003 U.S.-led invasion.

Suicide bombings are a particular hallmark of Sunni Islamist groups, some of which view Shi'ite Muslims as heretics.

The militants have increasingly used women for suicide bombings because they are less likely to be thoroughly searched by male guards, and because their voluminous robes can easily conceal vests packed with explosives and ball bearings or nails.

A sharp drop in the violence that swept Iraq after the 2003 U.S.-led invasion helped allies of Prime Minister Nuri al-Maliki score extensive victories in Iraq's Shi'ite south in a provincial election last month.

But the security gains are fragile, and suicide and car bomb attacks remain common.

Security sources have also warned that there could be an increase in attacks after Maliki's strong electoral showing, as political rivals and militants try to undermine the perception that the insurgency is on its last legs.