The U.S. military said Tuesday that three soldiers were killed the day before by a roadside bomb north of Baghdad, bringing to eight the number of troops who died that day.

An interpreter was also killed Monday along with the three soldiers when they were hit by the bomb in eastern Diyala province, a military statement said. Another soldier was injured in the attack. No other details were provided.

In another attack Monday in Baghdad, five American soldiers on a foot patrol were killed when a homicide bomber detonated his explosives vest after approaching them, the military said.

The names of the soldiers killed were withheld pending notification of their families, military officials said.

The attack showed the insurgents' ability to strike in the heart of the heavily fortified capital, as well as in restive Diyala province.

The attacks marked the deadliest day for American forces in Iraq since Sept. 10, when eight soldiers died in two road accidents and two Marines were killed fighting insurgents in Anbar province.

In the Baghdad attack, four of the soldiers died at the scene, and the fifth died later from wounds, the military said. Three other American troops and an Iraqi interpreter were wounded in the attack.

Iraqi police said two civilians were also killed in the bombing — the deadliest single attack against the U.S. military since Jan. 28 when five soldiers were killed in a roadside bomb in the northern city of Mosul.

The homicide bomber hit the soldiers after they had left their Humvees and were chatting with shop owners, an Iraqi police officer who witnessed the attack said on condition of anonymity as he wasn't authorized to speak to the media.

As part of the military's counterinsurgency plans, U.S. bases are now inside neighborhoods and more U.S. soldiers are getting out of their armored vehicles to patrol Baghdad on foot.

While the face-to-face contact builds goodwill, it also gives homicide bombers, who often slip past security vehicle checkpoints by walking, better access to striking soldiers.

According to military figures, attacks in Baghdad are down 75 percent since June 2007, largely because of a boost in U.S. troops, a cease-fire by the radical Shiite cleric Muqtada al-Sadr's Mahdi Army militia and the role of former Sunni militants and tribal groups who have switched sides to join U.S. forces against Al Qaeda in Iraq.

But some fear that violence in Baghdad and elsewhere will accelerate after the withdrawal of thousands of American troops.

The drawdown began last December with the departure of one brigade, numbering about 5,000 troops, dropping the overall U.S. troop level in Iraq to 158,000. More troops are set to leave by July, though it has yet to be decided whether further reductions will be made after that.

Monday's homicide bombing in Baghdad and the roadside bomb in Diyala were two of several deadly attacks across the country.

Earlier in the day, a female homicide bomber killed a U.S.-backed Sunni leader who formed a group to fight against Al Qaeda insurgents in central Iraq after his guards ushered her into the home without searching her.

A rare homicide car bomb Monday evening in the northern Kurdish city of Sulaimaniyah outside a hotel killed at least two people and wounded more than a dozen, hospital officials said.

In another attack, police on Monday found the bullet-riddled body of Basra's only neurologist — kidnapped earlier by gunmen.

On Tuesday in the northern city of Mosul, four police officers were killed by gunmen at a checkpoint, a provincial police official said on condition of anonymity as he was not authorized to speak to the media.

Gunmen also opened fire on a car carrying the deputy head of Mosul University, another police officer said on condition of anonymity. The academic escaped unharmed.