Female suicide bomber kills 35 at Baghdad shrine

* Many casualties are pilgrims from Iran

* Security tightened ahead of pilgrimage

By Aseel Kami and Waleed Ibrahim

BAGHDAD (Reuters) - A female suicide bomber infiltrated a crowd of Shi'ite pilgrims and blew herself up, killing at least 35 people and wounding at least 79 at a Shi'ite shrine in Baghdad Sunday, Iraqi officials said.

The bomber struck a checkpoint outside the Imam Moussa al-Kadhim shrine in Kadhimiya, a mainly Shi'ite area of Baghdad, as Shi'ites prepared for the Ashura holiday this week to mourn the death of Hussein, the grandson of the Prophet Mohammad.

Many of the casualties were pilgrims from Iran, security spokesman Major-General Qassim Moussawi said, underscoring the religious ties between the two majority Shi'ite countries.

"There were bodies everywhere, some of them missing legs and arms," said eyewitness Said Qassim, who was distributing food and drinks to pilgrims nearby at the time of the blast.

"I saw three women's bodies in bad shape and blood all over the place. This is a disaster."

"I can't understand how this suicide bomber reached this point. No one can get in here without going through seven checkpoints," he said.

Moussawi said 35 people were killed and 79 wounded. Other Iraqi security sources gave slightly higher casualty totals.

U.S. forces in Iraq came under an Iraqi mandate on January 1 in step with a pact that will require the withdrawal of the 140,000 U.S. troops by the end of 2011.

As the United States reduces its activities in Iraq, local forces are taking greater responsibility for security.

Sunday's bomb attack was a reminder of the challenges they face, almost six years after the U.S.-led invasion in 2003.

Violence has dropped dramatically from the peak of sectarian bloodshed in 2006-2007, but militants regularly stage bombings.

BOMBINGS BY FEMALES RISE

Moussawi said the government had ordered an investigation and a tightening of security surrounding the pilgrimage.

In the past year Sunni militants have increasingly dispatched women and girls as suicide bombers, a tactic aimed at thwarting security measures aimed at males. At least two dozen female bombers struck last year, killing scores of people.

Hundreds of thousands of Shi'ites will visit the holy city of Kerbala, 80 km (50 miles) southwest of Baghdad this week to mourn the death of Hussein in a 7th century battle, a day of passionate observance in the Shi'ite calendar.

Sunni militants have frequently targeted Shi'ite holy pilgrimages, which have become massive events since the fall of Saddam Hussein, who repressed them.

In 2004, at the first Ashura pilgrimage after Saddam's fall, Sunni militants killed more than 160 Shi'ite pilgrims in coordinated attacks on the Kadhimiya and Kerbala shrines.

Those strikes were an early portent of the sectarian fighting that would ravage Iraq over the next few years.

But despite the violence, pilgrimages continue to attract hundreds of thousands of worshippers, including many from Iran.

U.S. forces are slowly disengaging from day-to-day patrols as they prepare to withdraw forces from towns by mid-2009.

Sunday U.S. forces put the Iraqi government in charge of mainly Sunni Arab tribal guards in Diyala province north of Baghdad.

(Writing by Missy Ryan and Tim Cocks; Editing by Giles Elgood)