LONDON -- More mass graves have been found in two new locations in Iraq, together containing at least 4,000 bodies and perhaps as many as 15,000, human rights groups and a British news report said Tuesday.
If forensic experts confirm the findings, the mass graves at Hillah and the village of Muhammad Sakran would be the largest discovered since Saddam Hussein's regime collapsed in the U.S.-led war.
Residents using tractors and, later, their hands excavated bodies this week from graves in the central Iraqi town of Hillah, 60 miles south of Baghdad.
In a news release Tuesday, New York-based Human Rights Watch said the United States had known about the Hillah site since early May when the mayor of the city asked for help in guarding the graves, and U.S. forces refused.
"The U.S. government has not acted on important information about mass graves in Iraq," said Peter Bouckaert, of Human Rights Watch in Baghdad.
"The result is desperate families trying to dig up the site themselves -- disturbing the evidence for forensic experts who could professionally establish the identities of the victims."
The British Broadcasting Corp., which showed television footage of the grisly scene, said at least 3,000 bodies were exhumed.
It quoted unidentified human rights groups as saying the graves could contain 10,000 to 15,000 bodies. While Human Rights Watch confirmed the existence of the Hillah graves, it did not confirm estimates of the number of people buried there.
Another grave containing more than 1,000 Iraqis was recently found in Muhammad Sakran village, about 25 miles north of Baghdad, Human Rights Watch said.
Entifadh Qanbar, a spokesman for the Iraqi National Congress, a London-based exile group close to the U.S. military, said Tuesday in Baghdad that four graves found in Hillah could contain about 15,000 bodies.
"The citizens of the area are excavating these sites with a great deal of sadness and absolutely no assistance," Qanbar said. "Mothers and fathers are trying to identify their children by ID cards and the clothing they were last seen in." He called for help from U.S. civilian administrators.
The reports came a day after Iraqis pulled bodies from a newly discovered mass grave near Basra, the country's second-largest city. The site was believed to contain remains of up to 150 Shiite Muslims killed by Saddam's regime after a rebellion in 1999.
Human Rights Watch also criticized U.S. forces for not guarding the grave in Muhammad Sakran, which it said contained the remains of civilians executed by Saddam's regime in the 1980s.
The BBC said it did not know how or when the victims in the Hillah graves were killed. But it said they could have been Shiite Muslims massacred by Iraqi forces after a Shiite uprising against Saddam after the 1991 Gulf War.
BBC television footage of Hillah showed a tractor quickly excavating decomposed remains of men, women and children.
Large crowds of Iraqi men and women, many of them crying, picked through the mud by hand, pulling out skulls and body parts of decayed corpses and putting them in plastic bags.
Many victims appeared to have been executed by gunshot, the BBC reported.