U.S. and Iraqi forces launched a major offensive Friday in the town of Samarra, north of Baghdad, in what the military said was in response to repeated attacks by insurgents.

The U.S. 1st Infantry Division said an estimated 96 insurgents were killed. However, hospital officials say 80 people were killed and more than 100 were injured, including some civilians.

One U.S. soldier was killed and four were wounded during the operation.

The offensive began just after midnight and is still going on. It comes one day after a string of bombings across the country killed at least 51 people, including 35 children.

Just before dawn, U.S.-led forces moved into the city backed by tanks and warplanes, securing government and police buildings. In response, rebels launched mortar attacks and fired rocket-propelled grenades and rifles from the rooftops.

Water and electricity were cut off, and people were ordered to stay indoors as troops moved from house to house in search of insurgents.

Residents said they covered in their homes as tanks and warplanes pounded Samarra.

Dr. Khalid Ahmed of Samarra General Hospital said 80 bodies and more than 100 wounded were brought to the hospital. It is not clear how many of them were insurgents.

The military said the offensive was carried out in response to "repeated and unprovoked attacks by anti-Iraqi forces" against Iraqi and coalition forces.

Samarra is considered one of the top three rebel strongholds in Iraq, along with Fallujah and the Baghdad slum known as Sadr City.

Officials have previously said they would recapture cities taken over by insurgents before nationwide elections take place at the end of January. However, it's unclear if the raid in Samarra is part of that campaign.

The raid follows a deadly day across Iraq in which scores of children were killed as they collected candy from U.S. soldiers at a celebration for the reopening of a refurbished sewage plant.

The Tawhid and Jihad group, led by al Qaeda ally Abu Musab al-Zarqawi's, claimed responsibility for bloody attacks in Baghdad on Thursday, according to a statement posted on a militant Web site.

The authenticity of the statement could not be verified.

In other news, there are reports that two French journalists -- Christian Chesnot, 37, and George Malbrunot, 41 -- who have been held hostage in Iraq for more than a month could be released within hours.

Philippe Brett, an unofficial French negotiator, told Europe-1 radio that he was with the two journalists when the details for their release were finalized.

With files from The Associated Press