BAGHDAD (NYT) As Muslims in Iraq observe the 10-day holiday of Muharram, and Christians warily prepare for a subdued Christmas, episodes of violence erupted around the country on Wednesday, some of them aimed at worshipers of each faith.

There were four separate bomb attacks in Baghdad on Shiite pilgrims marching toward Karbala in observance of Muharram, and a fifth attack on people giving food and drinks to the marchers.

In East Baghdad, an improvised explosive device killed 3 marchers and wounded 28 others. A bomb attached to a motorcycle killed 1 pilgrim and wounded 7, while 7 more marchers were wounded in bombings south of Baghdad. A roadside bomb in the commercial Karada neighborhood exploded near people serving the marchers, killing 1 and wounding 4.

The pilgrimage to Karbala, culminating Sunday in the Day of Ashura, is one of the holiest Shiite observances, commemorating the martyrdom of Imam Hussein, grandson of the Prophet Muhammad, in 680 A.D. Saddam Hussein banned the pilgrimage, and it has been a target of attacks since his fall in 2003.

“They will not make us stop by making explosions here or there,” said Ahmed al-Saedi, 26, one of the marchers, who was not near the bombings. “They have tried with much bigger explosions and they saw what happened. We will never stop, so if they are strong enough, let them come face to face.”

The Iraqi government has promised to increase security for the pilgrims, deploying nearly 50,000 soldiers and police officers to Karbala and Najaf, where a million pilgrims are expected to converge this weekend.

In the northern city of Mosul, where sectarian violence has continued to run high, a bomb placed in a handcart opposite the Syrian Orthodox Church of St. Thomas killed two people, both Muslim, and damaged the church, which was built in 770. The attack followed threats to blow up churches at Christmas, and was the sixth attack on Christians in Mosul in less than a month. Threats and attacks against Iraqi Christians typically rise during the Christmas season.

After a relatively peaceful November, in which only 88 Iraqi civilians were killed in attacks, violence has increased this month, punctuated by a series of car bomb attacks on Dec. 8 that killed at least 121 people. The November total was the lowest since the American-led invasion of 2003, according to the Web site icasualties.org.

Iraqi police officers remain a favorite target of the attackers. In Abu Ghraib early on Wednesday morning, gunmen opened fire on a police checkpoint, killing four officers before escaping. In a similar shooting on Dec. 6, gunmen killed a police officer outside a guard room, then stormed the room and killed three more policemen inside.

The district commissioner of Abu Ghraib, Shaker Feza, blamed negligence among the security forces for the attacks. “They say that this place is a terrorist area and all the people who live here don’t deserve anything but to be killed,” Mr. Feza said.

Later in the day, in nearby Falluja, attackers placed a magnetic bomb on the armored car of a Sunni candidate for Parliament, Efan al-Essawi. The attack was the first on a candidate in the coming elections, according to the police.

Sheik Essawi, a Sunni Muslim running on the Iraqi Unity Alliance electoral list, was wounded but escaped serious harm. The sheik was also the head of the local Sunni Awakening, a group that formed to oppose Sunni insurgents and is credited for much of the reduction of violence in Iraq since 2007.

Another magnetic “sticky” bomb attached to a car in Falluja killed a man named Edham al-Mashhadani, whose brother runs the youth union in Anbar.

While violence has declined in most of the country, recent months have seen a rise in attacks in the areas west of Baghdad that include Abu Ghraib, Anbar and Falluja, early strongholds of the insurgency.

In unrelated incidents in Baghdad, a magnetic bomb attached to a minibus killed one person and injured three, and gunmen killed a police brigadier general in front of his home.

The Iranian ambassador to Iraq, Hassan Kazemi-Qomi, tried to play down a border dispute that erupted in the past week after Iranian soldiers briefly advanced into an oil field in territory claimed by Iraq, then withdrew. The ambassador said both governments agreed to 1975 treaties setting the border. He accused the news media of stirring up controversy before the election. “We have a unified vision regarding fulfilling the treaty,” he said. “There’s no disagreement between the two countries.” He added, “There are hidden hands who want to sabotage this relationship.”