BAGHDAD, Iraq – American troops opened fire near a checkpoint south of Baghdad after their convoy was hit by a roadside bomb, and a hospital official said yesterday at least eight people were killed in the second American attack in two days to have deadly results.

In other violence yesterday, an American soldier assigned to Task Force Baghdad was killed by a roadside bomb, while a Marine was killed in action in the volatile Anbar province.

Seven Ukrainian soldiers and one from Kazakhstan also died in an apparently accidental explosion at an ammunition dump south of Baghdad.

American officials said they had no information about the checkpoint shooting, which occurred overnight Saturday. Interior Ministry spokesman Colonel Adnan Abdul-Rahman said a roadside bomb hit an American convoy near a police checkpoint in Yussifiyah, nine miles south of Baghdad, and troops opened fire, killing two police officers and three civilians.

Dr. Anmar Abdul-Hadi of al-Yarmouk Hospital said eight people died in the attack and 12 were wounded.

American commanders recently announced a change in response to roadside bombings. Rather than pushing on after the blast, they now stop and try to engage the perpetrators, who may have detonated the explosives remotely.

Hours before the attack, America acknowledged dropping a 500-pound bomb on the wrong house during a search for terror suspects outside the northern city of Mosul. The military said in a statement that five people were killed.

The house’s owner, Ali Yousef, said 14 people died when the bomb hit at about 2 a.m. Saturday in Aitha, a town 30 miles south of Mosul. An Associated Press photographer at the scene said the dead included seven children and seven adults. The discrepancy between the death counts could not be reconciled.

Such attacks are exactly what America does not want prior to national elections scheduled for January 30.

Yesterday, Secretary of State Powell was asked on ABC’s “This Week” how he would define success in Iraq’s election, and he acknowledged concern about what will happen after the vote.

“Success is putting in place a government that is really elected and represents all of the people of Iraq…and creating an Iraqi security force that is able to protect the country and protect the people of Iraq,” he said.

An American soldier assigned to Task Force Baghdad was killed in a roadside bomb explosion, the military said without specifying where the attack occurred.

A Marine assigned to the 1st Marine Expeditionary Force also was killed in action yesterday while conducting security and stability operations in the western province of Anbar, which is home to the volatile city of Fallujah, according to a military statement released today. More details were not provided and identities were withheld pending notification of relatives.

Unknown assailants yesterday shot Samarra’s deputy police chief, Colonel Mohammed Mudhafir, as he drove alone, Samarra police Major Raed Ahmed said.

Few details were known about the explosion that killed the Ukrainian and Kazakh soldiers. The American military said late yesterday that the soldiers were cleaning up the ammunition dump.

Polish military spokesman Lieutenant Colonel Artur Domanski said the explosion occurred at about noon, about six miles south of Suwaira. Eleven soldiers were wounded – seven Ukrainians and four Kazakhs, he said.

Ukraine’s Defense Ministry said the soldiers were loading aviation bombs when one of the devices exploded.