BAGHDAD, Iraq (CNN) -- At least 100 people were killed and dozens were hurt in three separate suicide bombings in northern Iraq, police said Tuesday.
Three bombers detonated three trucks laden with explosives in three locations around 8 p.m., officials said.
The bombers targeted residential areas in the town, Qahtaniya and Mosul police said. Mosul police said U.S. military helicopters are helping to evacuate the wounded. Local television is asking for blood donations for the wounded.
The violence came on the same day as another brazen attack. Gunmen wearing army uniforms abducted five Oil Ministry officials from their Baghdad apartments, the Interior Ministry told CNN.
Abdul Jabber al-Wagga, a deputy oil minister, and four general managers were in a ministry compound along Palestine Street in southeastern Baghdad, when at least 60 gunmen driving in 17 vehicles stormed the site, wounding five guards in the clash, the Interior Ministry said.
It's not known whether the gunmen were soldiers or insurgents who somehow obtained army uniforms.
Assam Jihad, the Oil Ministry spokesman, also confirmed the incident and said the gunmen were dressed as "Iraqi security forces." He said "a number" of oil officials were taken as well.
The oil minister is Hussain al-Shahristani, a Shiite and a member of the ruling United Iraqi Alliance's Supreme Islamic Council of Iraq, a powerful Shiite political party.
Last week, Iran and Iraq signed agreements to build oil pipelines between the neighboring countries. Iraq would sell and transport crude oil to Iran, and Iran would sell and transport oil to Iraq from its refineries.
Many Sunnis in Iraq have been suspicious of Iran's intentions and activities in the country.
Hunt for al Qaeda
Earlier, the U.S. military announced a massive offensive against al Qaeda in Iraq militants in Diyala province -- now one of the major fronts in the war.
Operation Lightning Hammer began Monday. It includes about 10,000 coalition troops and 6,000 Iraqi security forces who are targeting "al Qaeda elements" who have fled the provincial capital of Baquba, according to a military statement on Tuesday.
Diyala is one of the so-called Baghdad belts, areas near the capital that have a strong insurgent presence. The military hopes to stave off attacks in the capital by defeating insurgents in those areas, which also include Anbar province to the west and the region south and southeast of Baghdad.
The announcement of the offensive came on the same day the military reported the deaths of nine more U.S. troops, five of them in a helicopter crash.
The CH-47 Chinook copter went down near Al Taqaddum Air Base during a check flight after undergoing maintenance, the military said in a press release.
The U.S. military also said that three U.S. soldiers died from injuries they incurred Monday when an explosion went off near their vehicle in Nineveh province in northern Iraq. And a U.S. soldier was killed Tuesday in western Baghdad, the military said.
The deaths bring to 3,699 the number of American military personnel, including seven defense contractors, who have died in the Iraq war. Forty-one U.S. troops have been killed in August.
In Baghdad, meanwhile, coalition forces targeted fighters that have been linked to the Mehdi Army, the militia of anti-American Shiite cleric Muqtada al-Sadr.
Coalition troops on Tuesday killed four insurgents and detained eight others in a raid in the Shiite neighborhood of Sadr City. Troops were targeting what it describes as "rogue" Mehdi Army militants who have "ties to illicit materials smuggled from Iran that have been used in extra-judicial killings."
The U.S. military also announced more operations against militias Monday in Baghdad.
Iraqi Special Operations troops that are advised by U.S. Special Forces have carried out "synchronized intelligence driven operations" that led to the detention of 12 "rogue" Mehdi Army insurgents.
The detained, who include several commander-level insurgents, are suspected of carrying out sectarian killings and roadside bombings.
One, a brigade commander, is suspected of transporting roadside bomb materiel from Iran into Iraq and is said to have ordered a bombing that killed two U.S. soldiers. He is also suspected of ordering militants "to set up illegal checkpoints to hunt down and assassinate Sunni citizens."
Another militant is accused of setting up a bomb in a market in June that killed two coalition soldiers.
Also Tuesday, at least eight people were killed and 10 others wounded when a suicide bomber driving a fuel tanker detonated on a bridge in the Taji area, north of Baghdad, an official with Iraq's Interior Ministry said. The attack partially collapsed the bridge that links Baghdad to northern Iraq. At least five vehicles plunged off the structure.
In central Kirkuk, a car bomb targeted a police patrol, killing one officer and wounding five people, including three police officers, according to the city's police.
CNN's Mohammed Tawfeeq and Raja Razek contributed to this report.