KARBALA, Iraq (CNN) -- A female suicide bomber apparently targeting Shiite worshippers killed at least 40 people and wounded at least 65 in Karbala on Monday, according to an Interior Ministry official.
Iraqi security forces gather around the site of a car bomb explosion in Baghdad on Monday.
The incident occurred one-half mile from the Imam Hussein shrine of Karbala.
Karbala is a Shiite holy city, and the Imam Hussein shrine is one of Shiite Islam's holiest locations. The shrine marks the burial spot of Hussein bin Ali, the grandson of the Prophet Mohammed, who was killed in battle nearby in 680.
No more information was immediately available about the blast southwest of the capital city, Baghdad.
Earlier Monday, in Baghdad, a roadside bomb exploded near an Iraqi police patrol, killing one officer and wounding another, the Interior Ministry told CNN.
A short time later, another roadside bomb exploded near an Iraqi police patrol on Palestine Street in eastern Baghdad, wounding four bystanders, a ministry official said.
The first attack took place about 8:30 a.m. in the upscale Mansour neighborhood, where law enforcement officials have come under frequent attacks in recent weeks.
Also Monday, two American soldiers were killed by a roadside bomb north of Baghdad, officials said.
The incident occurred about 12:20 p.m. as the soldiers were "conducting a route-clearance combat operation north of Baghdad," according to a news release.
The names of the soldiers were not immediately released.
Meanwhile, U.S. Vice President Dick Cheney arrived in the Iraqi capital Monday on an unannounced visit.
Cheney told reporters that the five years in Iraq since the war's start has been "well worth the effort."
He said he met with top Iraqi officials. He appeared at a news conference with Gen. David Petraeus, the top U.S. commander in Iraq, and Ryan Crocker, the U.S. ambassador to the country.
Cheney began a trip to the Middle East on Sunday with an official itinerary that listed stops in Oman, Saudi Arabia, Turkey, Israel and the West Bank, according to the White House. E-mail to a friend
CNN's Mohammed Tawfeeq contributed to this report.