BAGHDAD, Iraq -- Witnesses to the slaying of 24 Iraqi civilians by U.S. Marines in the western town of Haditha say the Americans shot men, women and children at close range in retaliation for the death of a Marine lance corporal in a roadside bombing.

Aws Fahmi, a Haditha resident who said he watched and listened from his home as Marines went from house to house killing members of three families, recalled hearing his neighbor across the street, Younis Salim Khafif, plead in English for the lives of himself and his family.

"I heard Younis speaking to the Americans, saying: 'I am a friend. I am good,' " said Mr. Fahmi. "But they killed him, and his wife and daughters."

The 24 Iraqi civilians slain Nov. 19 included children and the women trying to shield them, witnesses told a Washington Post special correspondent in Haditha this week and U.S. investigators said in Washington.

The girls killed inside Mr. Khafif's house alone were aged 14, 10, 5, 3 and 1, according to death certificates.

Two U.S. military boards are investigating the incident as potentially the gravest violation of the law of war by U.S. forces in the 3-year-old conflict in Iraq. The U.S. military ordered the probes after Time magazine presented military officials in Baghdad this year with the findings of its own investigation, based on accounts from survivors and on a videotape shot by an Iraqi journalism student at Haditha's hospital and inside houses.

A Naval Criminal Investigative Service investigation into the killings and a separate military probe into an alleged coverup afterward are slated to end in the next few weeks. Marines have briefed members of the Senate Armed Services Committee and other officials about the findings; some officials who have been briefed say the evidence is damaging.

Charges of murder, dereliction of duty and making a false statement are likely, people familiar with the case said yesterday.

"Marines overreacted ... and killed innocent civilians in cold blood," said one of those briefed, Pennsylvania's Rep. John Murtha, D-Johnstown, a former Marine who maintains close ties with senior Marine officers despite his opposition to the war.

Haditha is one of a chain of farm towns on the Euphrates River where U.S. and Iraqi forces have battled foreign and local insurgents without resolution for much of the war.

The first account of the killings there was a false or erroneous statement issued the next day, Nov. 20, by a U.S. Marine spokesman from a Marine base in Ramadi: "A U.S. Marine and 15 civilians were killed yesterday from the blast of a roadside bomb in Haditha. Immediately following the bombing, gunmen attacked the convoy with small-arms fire. Iraqi Army soldiers and Marines returned fire, killing eight insurgents and wounding another."

The incident was touched off when a roadside bomb struck a supply convoy of Kilo Company, 3rd Battalion, 1st Marine Regiment.

The explosion killed Lance Cpl. Miguel Terrazas, 20, from El Paso, Texas, who was on his second tour in Iraq. Following in the footsteps of two Marine uncles and a Marine grandfather, Cpl. Terrazas had planned to go to college when it was all done, his family said.

Insurgents planted the bomb off one of Haditha's main streets, putting it on a side road, between two vacant lots, to try to avoid killing -- and further alienating -- Haditha's civilians, residents said. It went off at 7:15 a.m.

Cpl. Terrazas was driving the Humvee. He died instantly. Two other Marines in the convoy were wounded.

"Everybody agrees that this was the triggering event. The question is, what happened afterward?" said Paul Hackett, an attorney for a Marine officer with a slight connection to the case.

Descriptions of events provided to The Post by witnesses in Haditha could not be independently verified, though their accounts of the number of casualties and their identities were corroborated by death certificates.

In the first minutes after the shock of the blast, residents said, silence reigned on the street of walled courtyards, brick homes and tiny palm groves. Marines appeared stunned, or purposeful, as they moved around the burning Humvee, witnesses said.

Then one of the Marines took charge, shouting, said Mr. Fahmi, who was watching from his roof. Mr. Fahmi said he saw the shouting Marine direct other Marines into the house closest to the blast, about 50 yards away.

It was the home of Abdul Hamid Hassan Ali, 76. Although he had used a wheelchair since diabetes forced a leg amputation years ago, Mr. Ali was always one of the first on his block to go out every morning, scattering scraps for his chickens and hosing the dust of the arid western town from his driveway, neighbors said.

In the house with Mr. Ali and his 66-year-old wife, Khamisa Tuma Ali, were three middle-aged men of their family, at least one daughter-in-law and four children -- 4-year-old Abdullah, 8-year-old Iman, 5-year-old Abdul Rahman and 2-month-old Asia.

Marines entered shooting, witnesses recalled. Most of the shots -- in Mr. Ali's house and two others -- were fired at such close range that they went through the bodies of the family members and plowed into walls or the floor, doctors at Haditha's hospital said.

A daughter-in-law, identified as Hibbah, escaped with Asia, survivors and neighbors said. Iman and Abdul Rahman were shot but survived. Four-year-old Abdullah, Mr. Ali and the rest died.

Mr. Ali took nine rounds in the chest and abdomen, leaving his intestines spilling out of the exit wounds in his back, according to his death certificate.

The Marines moved to the house next door, Mr. Fahmi said. Inside were 43-year-old Mr. Khafif, 41-year-old Aeda Yasin Ahmed, an 8-year-old son, five young daughters and a 1-year-old girl staying with the family, according to death certificates and neighbors.

The Marines shot them at close range and hurled grenades into the kitchen and bathroom, survivors and neighbors said later.

Mr. Khafif's pleas could be heard across the neighborhood. Four of the girls died screaming.

Only 13-year-old Safa Younis lived -- saved, she said, by her mother's blood spilling onto her, making her look dead when she fell, limp, in a faint.

Townspeople led a Washington Post reporter this week to the girl they identified as Safa. Wearing a ponytail and tracksuit, the girl said her mother died trying to gather the girls. The girl burst into tears after a few words. The older couple caring for her apologized and asked the reporter to leave.

Moving to the third house in the row, Marines burst in on four brothers, Marwan, Qahtan, Chasib and Jamal Ahmed. Neighbors said the Marines killed the four brothers together.

Marine officials later said one of the brothers had the only gun found among the three families, although there has been no known allegation that the weapon was fired.

Meanwhile a separate group of Marines found at least one other house full of young men. The Marines led the men in that house outside, some still in their underwear, and away to detention.

The day's final victims happened upon the scene inadvertently, witnesses said. Four male university students -- Khalid Ayada al-Zawi, Wajdi Ayada al-Zawi, Mohammed Battal Mahmoud and Akram Hamid Flayeh -- had left the Technical Institute in Saqlawiyah for the weekend to stay with one of their families on the street, said Mr. Fahmi, a friend of the young men. He said Haditha taxi driver Ahmed Khidher was bringing them home.

According to Mr. Fahmi, the young men and their driver turned onto the street and saw the wrecked Humvee and the Marines. Mr. Khidher threw the car into reverse, trying to back away at full speed, Mr. Fahmi said, and the Marines opened fire from about 30 yards away, killing the men inside the taxi.

After the killings, Mr. Fahmi said, more Americans arrived at the scene. They shouted among themselves. The Marines cordoned off the block; then and for at least the next day, Marines would file into the houses, look around and come out.

At some point Nov. 19, Marines in an armored convoy arrived at Haditha's hospital. They placed the victims' bodies in the garden of the hospital and left without explanation, said Mohammed al-Hadithi, one of the hospital officials who helped carry the bodies inside. By some accounts, some corpses were burnt.

The Marines of Kilo Company, 3rd Battalion, 1st Marines have rotated back home, to California.