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

In southern Iraq, meanwhile, a roadside bomb hit a bus that was traveling from Basra to Nasiriyah, killing at least 16 civilians on board, according to a Nasiriyah policeman who spoke on condition of anonymity as he wasn't authorized to release the information.

At least 22 others were wounded in the attack, which took place about 50 miles south of Nasiriyah.

An interpreter also was killed on Monday along with three soldiers when they were hit by the bomb in eastern Diyala province, a military statement said. Another soldier was wounded in the attack.

On Monday in Baghdad, five American soldiers on a foot patrol were killed when a suicide bomber detonated his explosives vest.

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.

The attack in Baghdad showed the insurgents' ability to strike in the heart of the heavily fortified capital, as well as in restive Diyala province. Three other American troops and an Iraqi interpreter also were wounded in the Baghdad attack.

Iraqi police said two civilians also were 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 suicide bomber hit the soldiers after they had left their Humvees and were chatting with shop owners.