BAGHDAD, Iraq (CNN) -- A suicide bomber killed at least 40 Shiite pilgrims and wounded 60 others Sunday as the pilgrims made their way to Karbala to commemorate one of the holiest days of the Shiite calendar, the Interior Ministry said.

Women and children were among the casualties, the official said. Most of those killed or wounded were pilgrims.

It marked the second deadly attack on pilgrims Sunday, the official said.

The bomber detonated an explosive vest in Iskandariya about 3 p.m. while the pilgrims were en route to Karbala for al-Arbaeen, the official said. The holiday falls on Wednesday.

Earlier Sunday, militants armed with guns and grenades attacked a group of pilgrims in southern Baghdad, killing three people and wounding more than 30 others, officials said.

The wounded included two police officers, the ministry said.

Iraqi officials had expected problems for pilgrims and issued a ban on carts in Baghdad on Friday.

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A Defense Ministry official said the ban was ordered after a horse-drawn carriage blew up near a restaurant in the Karrada district, killing three civilians and wounding six others.

There was no indication when the ban would be lifted.

Every year, thousands of pilgrims amass in Karbala for al-Arbaeen, which commemorates the end of a 40-day mourning period for Imam Hussein, the grandson of the Prophet Mohammed.

Hussein is one of the most revered Shiite martyrs. He died in battle in the 7th century, and is buried in Karbala, about 60 miles southwest of Baghdad. Karbala's main holy site is the gold-domed Imam Hussein Shrine.

Violence struck northern Iraq on Sunday as well. In Hawija, southwest of Kirkuk, a bomb exploded outside a building where tribal leaders were meeting, killing one. Nine others were injured, including a local council leader, police said.

The person killed was an Awakening Council member. Groups such as Concerned Local Citizens, Sons of Iraq and Awakening Councils are helping the U.S. and Iraqi militaries fight al Qaeda in Iraq.

The Sunday meeting was aimed at bringing together tribal leaders to sort out differences and cooperate with one another.

In other developments:

• Eight Turkish soldiers and 33 Kurdish rebels were killed Sunday in fighting in northern Iraq, Turkey's military said. Turkey began a ground operation against the rebels Thursday -- its first significant ground offensive into Iraq since the fall of Saddam Hussein. So far, 15 Turkish soldiers and 112 Kurdish rebels have been killed, according to figures from Turkey's military.

• Prime Minister Nuri al-Maliki, 57, is flying to London on Sunday for medical checkups, two months after doctors examined him for an unspecified condition, his office said. However, an official with his office said he underwent medical tests related to exhaustion. Al-Maliki's office has said there is no cause for concern. After al-Maliki's visit to London in December, doctors recommended that he return for periodic checkups, his office said.

• A truck, disguised as a relief vehicle and containing 2½ tons of explosives, was removed from a Mosul neighborhood earlier this month after residents reported it to U.S. troops, the military said Saturday. The truck had markings like those used by the Red Crescent Society, and it also had a "suicide switch" in the cab, an officer said. E-mail to a friend

CNN's Mohammed Tawfeeq and journalist Andrew Finkel contributed to this report.

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