Residents gave new details Monday about the shootings of civilians in a western Iraqi town, where the U.S. military is investigating allegations of potential misconduct by American troops last November.

The residents said troops entered homes and shot and killed 15 members of two families, including a 3-year-old girl, after a roadside bomb killed a U.S. Marine.

The military, which announced Friday that a dozen Marines are under investigation for possible war crimes in the Nov. 19 incident, said in a statement Monday that a videotape of the aftermath of the shootings in Haditha, 140 miles northwest of Baghdad, was presented in support of the allegations.

The charges against the Marines were first brought forward by Time magazine, which reported this week that it obtained a videotape two months ago taken by a Haditha journalism student that shows the dead still in their nightclothes.

The magazine report mirrored what was told independently to The Associated Press by residents who described what happened as "a massacre." However, Time said the available evidence did not prove conclusively that the Marines deliberately killed innocents.

A military spokeswoman said Monday the allegations were being taken "very seriously."

Khaled Ahmed Rsayef, whose brother and six other relatives were killed, said the roadside bomb exploded at about 7:15 a.m. in the al-Subhani neighborhood, heavily damaging a U.S. Humvee.

A U.S. military statement in November described it as an ambush on a joint U.S.-Iraqi patrol that left 15 civilians, eight insurgents and a U.S. Marine dead in the bombing and a subsequent firefight. The statement said the 15 civilians were killed by the blast, a claim residents denied.

The residents said the only shooting done after the bombing was by U.S. forces.

"American troops immediately cordoned off the area and raided two nearby houses, shooting at everyone inside," said Rsayef, who did not witness the events but whose 15-year-old niece says she did. "It was a massacre in every sense of the word."

Rsayef and another resident, former city councilman Imad Jawad Hamza, who spoke with hospital officials and residents, said the first house to be stormed was that of Abdul-Hamid Hassan Ali, which was near the scene of the bombing.

Ali, 76, whose left leg was amputated years ago because of diabetes, died after being shot in the stomach and chest. His wife, Khamisa, 66, was shot in the back. Ali's son, Jahid, 43, was hit in the head and chest. Son Walid, 37, was burned to death after a grenade was thrown into his room, and a third son, 28-year-old Rashid, died after he was shot in the head and chest, Rsayef and Hamza said.

Also among the dead were son Walid's wife, Asma, 32, who was shot in the head, and their son Abdullah, 4, who was shot in the chest, Rsayef and Hamza said.

Walid's 8-year-old daughter, Iman, and his 6-year-old son, Abdul-Rahman, were wounded and U.S. troops took them to Baghdad for treatment. The only person who escaped unharmed was Walid's 5-month-old daughter, Asia. The three children now live with their maternal grandparents, Rsayef and Hamza said.

Rsayef said those killed in the second house were his brother Younis, 43, who was shot in the stomach and chest, the brother's wife Aida, 40, who was shot in the neck and chest while still in bed where she was recuperating from bladder surgery. Their 8-year-old son Mohammed bled to death after being shot in the right arm, Rsayef said.

Also killed were Younis's daughters, Nour, 14, who was shot in the head; Seba, 10, who was hit in the chest; Zeinab, 5, shot in the chest and stomach; and Aisha, 3, who was shot in the chest. Hoda Yassin, a visiting relative, was also killed, Rsayef and Hamza said.

The only survivor from Younis's family was his 15-year-old daughter Safa, who pretended she was dead. She is living with her grandparents, Rsayef said.

The troops then shot and killed four brothers who were walking in the street, Rsayef and Hamza said, identifying them as the sons of Ayed Ahmed — Marwan, Qahtan, Jamal and Chaseb.

U.S. troops also shot dead five men who were in a car near the scene, Hamza and Rsayef said. They identified the five as Khaled Ayad al-Zawi and his brother Wajdi as well as Mohammed Battal Mahmoud, Akram Hamid Flayeh and Ahmad Fanni Mosleh.

It was not clear if the nine men were involved in the attack as the military statement said.

According to the Defense Department, the Marine who was killed near Haditha that day was Lance Cpl. Miguel Terrazas, 20, of El Paso, Texas. He was assigned to 3rd Battalion, 1st Marine Regiment, 1st Marine Division, I Marine Expeditionary Force.

Dr. Walid al-Hadithi, chief physician at Haditha General Hospital, said that about midnight the day of the attack, two U.S. Humvees arrived at the hospital — one carrying the bodies of men and the other those of women and children.

"They (the Marines) told me the women and children were shot in their homes, and they added that the men were saboteurs," al-Hadithi said. He said he was given a total of 24 bodies. "All had bullet wounds."

Time magazine said its investigation showed that walls and ceilings in both houses were pockmarked with shrapnel and bullet holes as well as sprays of blood. The video did not show any bullet holes on the outside of the houses — holes that might support the military report of a gunbattle.

The military, after being shown the videotape in January, concluded civilians were killed by Marines, Time said, victims of "collateral damage."

A human rights group condemned the shooting of civilians in Haditha.

"Regrettably the American military goes too far in their strikes against civilians because they consider many civilian areas as targets," said Wail al-Tai of the Baghdad Center for Human Rights Studies.

Human Rights Minister Nirmeen Othman would not comment on the incident.

U.S. military spokeswoman Lt. Col. Michelle Martin-Hing issued a statement Monday in response to an e-mail query from the AP:

"We take these allegations very seriously, and I believe the fact that two additional investigations are ongoing concerning this incident clearly demonstrates that. The incident in question was the first in a series of engagements that day that began when the Marine patrol was ambushed in a residential neighborhood with an IED followed immediately by small arms fire from multiple directions."

Saying Marines tracked insurgents for more than five hours, Martin-Hing said "the investigation will examine whether any rules of engagement were violated in the Marines' response to the insurgent attack. We are committed to thoroughly investigating this incident."

Lt. Gen. Peter Chiarelli, the No. 2 U.S. commander in Iraq, said about 12 Marines were under investigation for possible war crimes in the incident. He said the case was referred to the Naval Criminal Investigative Service; it was unclear which other ongoing investigation Martin-Hing was referring to in her statement.