BEIJI, Iraq — Investigators believe a group of U.S. soldiers suspected of raping an Iraqi woman, then killing her and three members of her family plotted the attack for nearly a week, a U.S. military official said Saturday.

Up to five soldiers are being investigated in the March killings, the fifth pending case involving alleged slayings of Iraqi civilians by U.S. troops.

The Americans entered the Sunni Arab's family home, separated three males from the woman, raped her and burned her body using a flammable liquid in a cover-up attempt, a military official close to the investigation said. The three males were also slain.

The soldiers had studied their victims for about a week and the attack was "totally premeditated," the official said on condition of anonymity because the investigation was ongoing. The family had just moved into the home in the insurgent-riddled area around Mahmoudiya, 20 miles south of Baghdad.

The U.S. military issued a terse statement about the killings Friday, saying only that Maj. Gen. James D. Thurman, commander of the 4th Infantry Division, ordered a criminal investigation into the alleged slaying.

U.S. officials said they knew of the deaths but thought the victims were killed in sectarian violence. But Mahmoudiya police Capt. Ihsan Abdul-Rahman said Iraqi officials received a report on March 13 alleging that American soldiers had killed the family.

BAGHDAD, Iraq — A parked car bomb exploded at a popular outdoor market Saturday in a Shiite slum in Baghdad, killing at least 66 people and wounding dozens, authorities said. It was the bloodiest attack to hit Iraq since the death of terror leader Abu Musab al-Zarqawi.The blast, which occurred around 10 a.m. when the Sadr City market was packed with shoppers, destroyed the stalls where food and clothes are peddled and sent up a plume of gray smoke. Flames shot out the windows of several scorched cars.Rasoul Zaboun, an official from the Imam Ali Hospital in Sadr City, said 66 people were killed and 87 wounded.

GAZA CITY, Gaza Strip — Palestinian militants holding an Israeli soldier issued a new set of demands Saturday, calling for the release of 1,000 prisoners and a halt to Israel's military offensive in Gaza. But Israel rejected them.Meanwhile, the Palestinian deputy minister of prisoner affairs, Ziad Abu Aen, said mediators had told him the Israeli soldier, Cpl. Gilad Shalit, was injured in the Sunday raid in which he was captured but was alive.The latest militant demands were issued as Israel kept up pressure on the Palestinians, launching airstrikes throughout Gaza for a fourth straight night and firing artillery rounds at the southern and northern parts of the coastal strip from tanks and navy gunboats. One of the targets was a Hamas training camp.