BAGHDAD — A suicide bomber struck Shiites as worshippers prepared Thursday for their most important holiday, killing at least 11 at a mosque in violent Diyala province _ one day after a similar attack by a woman in a nearby village.
Police and eyewitnesses said one of the victims had intercepted the bomber when he saw him making his way through the crowd. "Stranger, stranger," he shouted as he grabbed the bomber, who instantly detonated the blast.
A spike in bombings in recent weeks is chipping away at security gains made over the past six months, when levels of violence dropped nationwide. Many of the attacks have targeted Sunnis who have turned against the main insurgent group, al-Qaida in Iraq.
Authorities fear the Shiite religious events _ marking the death of a 7th century Shiite saint _ could increasingly fall into the cross-hairs of Sunni extremists.
Iraqi officials stepped up security across much of the country to protect the Shiite processions for the holiday period, culminating in events known as Ashoura. In Baghdad, a 48-hour ban on heavy vehicles went into effect, and Iraqi army troops and police were out in greater numbers on patrols and checkpoints.
The heaviest security was in the holy city of Karbala south of Baghdad, where some 30,000 troops watched over hundreds of thousands of pilgrims performing Ashoura rites.
Sunni Arab militants have repeatedly targeted Ashoura processions, with hundreds killed by mortar shelling or car bombings since 2003. Ashoura commemorates the battlefield death of Imam Hussein, whose tomb is in Karbala, about 60 miles from Baghdad.
Ashoura is essentially a mournful occasion. But Iraq's majority Shiites have used it to showcase their dominant status after decades of oppression under Saddam Hussein's Sunni-led regime. Hundreds of thousands march to Karbala or organize processions in their hometowns.
Militant Sunnis look upon Ashoura with contempt. They believe some of its rituals, like self flagellation and the use of images, amount to pagan worship and violate Islamic teachings.
Thursday's bombing took place in the Shiite neighborhood of Shafta on the southern outskirts of Baqouba, Diyala's provincial capital about 35 miles northeast of Baghdad.
The bomber detonated his explosives among crowds of Shiites at the door of the mosque, targeting men beating their chests in Ashoura rites, a police official said, speaking on condition of anonymity because he feared reprisals.
The attack killed 11 people and wounded 15, according to hospital officials, speaking on condition of anonymity because they were not authorized to release the information.
"Such a painful event will not deter us from continuing Ashoura ceremonies," said a witness, who referred to himself only as Abu Salam. "We do not want further Shiite-Sunni strife in our area."
It was the second deadly suicide attack against Ashoura crowds in as many days in Diyala _ one of Iraq's most violent provinces and now at the front lines of a U.S.-led offensive to dislodge al-Qaida in Iraq insurgents.
Wednesday's bombing, in a Shiite village nine miles south of Baqouba, was carried out by a female suicide bomber _ the fourth such woman kamikaze in Diyala since November. Nine people were killed.
Ashoura observances have been going on for about a week and are scheduled to climax Friday night through midday Saturday.
In Baghdad, where Shiite influence has significantly increased since 2003, streets were filled with Shiite banners and poster images of Imam Hussein. The images were hoisted on stores, government buildings, homes and even date palms and utility poles.
A narrow roll of black cloth hung from the top floor down to street level at the 10-story headquarters of the Baghdad city government, formerly the Saddam-era information ministry.
Rice, lamb and black tea sweetened with sugar were served free of charge in colorful tents erected on quiet streets in Shiite neighborhoods and some mixed areas under the protection of Iraqi troops and police. Shiite hymns narrating the death of Imam Hussein in the Karbala battle blared from giant speakers in many parts of the city.
In Karbala, Brig. Raed Shawkat, the police chief, said Iraqi helicopters were supporting the 30,000 Iraqi troops already deployed in the city and in groves and deserts surrounding it. About 300 snipers have taken position on rooftops close to the shrine of Imam Hussein and the nearby tomb of his brother Abbas, he said.
With al-Qaida's recent use of female suicide bombers, authorities deployed 500 policewomen in Karbala to search female pilgrims.
The U.S. military announced Thursday a second major wave of air strikes in a week against al-Qaida in Iraq positions southeast of Baghdad.
It said 10,000 pounds of munitions were dropped Wednesday on suspected bunkers used as insurgent training sites. Last week, warplanes dropped 40,000 pounds of munition on al-Qaida positions in the same area in one of the most intense air raids since the Iraq war began.
Associated Press writer Sameer N. Yacoub contributed to this report.