Iraq's Interior Ministry says a suicide attack south of Baghdad has killed at least six civilians.

Ministry spokesman Brig. Gen. Saad Maan says six suicide bombers tried Monday to infiltrate the holy Shiite city of Karbala, but security forces managed to kill five of them. Maan added that the sixth bomber broke into a house where he blew up himself, killing six and wounding six.

Hundreds of thousands of faithful Shiites have been walking to Karbala to commemorate the end on Sunday of the 40-day mourning period of the seventh century death of Imam Hussein, Prophet Muhammad's grandson. The city is located is some 90 kilometers (55 miles) south of Baghdad.

No group claimed responsibility, but suspicion fell on Sunni religious extremists who consider Shiites as heretics.