At least 32 people have died in an apparent suicide bomb attack on a group of Shi'ite pilgrims near the city of Basra in southern Iraq.

Police and medics say around 100 people were injured in the blast near a police checkpoint on the route to a Shi'ite shrine.

The attacks took place as many Shi'ites journeyed to a shrine near Basra to observe the end of an annual period of mourning. Security is high due to a series of attacks on Shi'ites in recent weeks.

Tensions between Shi'ite and Sunni Muslims in Iraq are high, especially since the withdrawal of U.S. troops from the country last year.

Under the regime of executed dictator Saddam Hussein, the government was dominated by Sunni Muslims.

Iraq's present government, headed by Shi'ite Prime Minister Nuri al-Maliki, is dominated by Shi'ites, but includes Sunnis and Kurds in a fragile power-sharing government that is rife with sectarian tensions.

More than 100 people have been killed in a spate of attacks on Shi'ites since the government issued an arrest warrant for Sunni Vice President Tariq al-Hashemi last month, on charges he ran a death squad.

Hashemi has denied the charges and fled to Iraq's autonomous Kurdish region to avoid detention.