A female suicide bomber on Thursday killed at least 18 Shiite pilgrims on their way to the holy city of Karbala, an Iraqi police source said.

The attack, near the town of Iskandariya, some 60 km south of Baghdad, also wounded 75 people, the source said on condition of anonymity.

Thousands of pilgrims were traveling to the holy city of Karbala, about 110 km south of the capital, to commemorate the birth in the 9th century of the Imam Muhammad al-Mahdi, last of 12most revered Shiites Imams.

The suicide blast was the most critical after three female attackers killed more than 24 and injured over 62 on July 28 during a Shiite pilgrimage gathering in Baghdad.

Violence has dramatically dropped in Iraq, the U.S. military said, hitting a four-year low.

But sporadic suicide or car bombing attacks are still haunting the Iraqis and creating remarkable casualties.

Meanwhile, suicide explosions staged by women have increased as they are less subject to check and suspicion.

(Xinhua News Agency August 15, 2008)