Evidence of mass graves have already been found in Iraq
A number of mass graves have been found by human rights workers in Iraq - containing what appears to be the bodies of up 100 civilians
The seven sites were found over a short period of time in the Basra area, Amnesty International said on Friday.
The organisation said many of the 40 bodies so far uncovered may have been killed during a uprising against Saddam Hussein in 1991.
Last month hundreds of skulls and bundles of bone in strips of military uniform were found by British soldiers at an abandoned Iraqi military base near al-Zubayr in southern Iraq.
Amnesty is calling for a full and proper investigation to find out whether the grave sites are in any way linked and to establish the identities of those killed.
The group wants US and British forces to establish
security zones around the mass graves to protect the sites, saying it should be the "duty of the occupying force".
It believes some of the dead were killed during a Shiite Muslim uprising in southern Iraq in 1991. Others may have been the target of political assassination.
Spokeswoman Judit Arenas Licea said: "We visited seven graves in three days [containing] from one
person to 40 bodies," she said.
"The clothes indicated they were civilians."
Amnesty's Ghanim Alnajar said local people led them to the site, after they had been digging and in some cases finding the bodies of relatives.
"We couldn't carry on; we needed more equipment. We've seen 25 to 26 bodies, but I think there was 100 of them on the site," he told news agency AFP.
The main grave site was near Abul Khasim, 20 kilometres (13 miles) south of Basra.
It appeared bodies may have been driven by truck to the site, while other victims were reportedly executed on the
Amnesty International wants the British Army to give protection to the site and says it has received reports of British soldiers removing a body from the graves.
"We have to ensure these graves are treated correctly and that the evidence is preserved, so that proper investigations can be made into any human rights abuses," Lesley Warner, of Amnesty International told BBC News Online.
She said AI also wanted a UN commission of experts to be involved in the re-establishment of Iraq's judicial system.
"This needs to be done at the beginning and does need international involvement working with Iraqi civil authorities," she said.