A police source said on Sunday that the victims' identities are unclear and the bodies appeared to have been there for some time.
They were found on Friday and are now in a Baghdad mortuary, another police officer said.
A leading Sunni organisation, the Association of Muslim Scholars, issued a statement on Sunday, however, saying that 30 bodies had been found at the firing range.
It said one body was identified as belonging to a Sunni Arab, but it gave no details.
In a separate find in Baghdad, Iraqi police announced the discovery of six more bodies in Baghdad, most of them tortured before being executed.
Three bodies, including those of two tortured policemen brothers, were found in eastern Baghdad, police said on Monday, and another three unidentified, blindfolded and tortured bodies were found in the north of the capital.
US soldiers killed
Meanwhile, the US military has announced the deaths of four American soldiers, killed in two separate roadside bomb attacks during combat operations west of Baghdad.
It said the first two soldiers were killed on Saturday when a bomb exploded near their vehicle during combat operations 19km outside Amiriyah, about 40km west of Baghdad.
The soldiers were assigned to the 155th Brigade Combat Team, II Marine Expeditionary Force.
More than 1700 US soldiers have
been killed since March 2003
The other two soldiers, who were assigned to the 2nd Marine Division, II Marine Expeditionary Force, were killed on Saturday when their vehicle struck a bomb during a combat operation about 29km southwest of Taqaddum, west of Baghdad.
As of Sunday, at least 1701 members of the US military have died since the beginning of the Iraq war in March 2003.
Spate of attacks
In the town of al-Shirqat, south of the northern city of Mosul, a truck driver and his assistant were killed when an explosive device, which was planted amid trucks transporting supplies to US troops, went off, Aljazeera reported.
And in al-Siniya area, west of the Iraqi town of Baiji, three Iraqi soldiers were wounded when their patrol was targeted, Aljazeera added.
In the west of the country, US forces said they killed about "40 insurgents" in air strikes on Saturday near Qaim on the Syrian border, a stronghold of anti-US rebels.
At the scene on Sunday, it was hard to determine the number and identity of casualties. Local people denied fighters had been there, but prevented journalists from visiting some destroyed houses.
"Before the elections there were certain groups that used to say that Iraq is under occupation and they have a right to resist.
But now I believe
this situation no
Iraqi Prime Minister's spokesman
Also in the west, three civilian drivers were killed on the main desert highway between Baghdad and Jordan when rebels and US troops exchanged fire, a local mayor said.
Seven civilians were wounded when a roadside bomb exploded close to an Iraqi army patrol near Falluja, 50km west of Baghdad, which US forces wrested from Sunni fighters last November.
Separately near Falluja, a police captain, Saadi Abed al-Jumaili, was shot and killed as he left his home on Sunday morning, relatives said.
Furthermore, three mortar rounds landed close to a house in Baghdad where the funeral of the mother of a senior Iraqi army commander, Major-General Rashid Fleya, was taking place, police said.
One mourner was killed and two wounded. When police were trying to find the assailants, a bomb went off that wounded 10 people, five of them policemen, the police source added.
In other news, the new Shia-led government said on Sunday that some anti-US groups had agreed on the need to join Iraq's political life and called on them lay down their guns.
Laith Kubba, a spokesman for Prime Minister Ibrahim al-Jaafari, said some groups feel they no longer needed to carry out their "resistance" following the 30 January national elections and the transfer a year ago of sovereignty from US-led authorities to an Iraqi government.
Bombings have blighted Iraq
since the US-led invasion
"Of course before the elections there were certain groups that used to say that Iraq is under occupation and they have a right to resist," Kubba said.
"But now I believe this situation no longer exists, and many groups are agreeing on the concept to take part in the political process," he added.
"So, now is the right time for any group to lay down their weapons and take part in the process."
Kubba was referring to Iraqi groups opposed to the continued presence of US-led forces in the country, but not foreign fighters like Jordanian Abu Musab al-Zarqawi, head of the al-Qaida in Iraq group, and his Iraqi allies.
More than 12,000 Iraqi civilians have been killed in violence during the past 18 months, according to Interior Ministry figures.
On Saturday, Muwafaq al-Rubie, the country's national security adviser, announced that the trial of former president Saddam Hussein would be held before a referendum on the new Iraqi constitution.
"Saddam will be tried on crimes he has committed, and he will have the right to defend himself against the charges filed against him," he said.
"The Iraqi people, and the rest of the world, will be able to see the trial live on television," he added.