In a separate incident a car bomb exploded near a police patrol in central Baghdad killing two and injuring eight people, an Interior Ministry official said.
"Two charred bodies that are difficult to identify were found at the scene of the attack," the official said, adding that one of those hurt was a policeman.
Initial reports spoke of a car bomber, but the official later said a parked car was detonated by remote control.
Five Iraqi civilians from the same tribe, including a child, were gunned down on Tuesday near Suwairah, south of Baghdad, medical and security sources said.
"The bullet-riddled bodies of five people were brought to us," said doctor Hussein Darwish from the hospital in Suwairah, a town near the village of Hurriyah, where the attack occurred.
Police in Suwairah confirmed that five people from the same tribe had been shot dead but provided no further details.
Armed men opened fire on a convoy carrying conservative Shia legislator Salamah al-Khafaji, one of the most prominent women in Iraq's new parliament, critically injuring four of her bodyguards.
Al-Khafaji was driving from Baghdad to the Shia holy city of Najaf, south of the capital, when the attempt took place, according to her spokesman. She was not injured.
Two people were killed in a car
explosion in central Baghdad
"It was a motorcade of four cars driving to Najaf. They were subjected to gunfire, four of guards were critically injured", said spokesman Bahaa Hassan Hamida.
Al-Khafaji survived an assassination attempt in May 2004 that killed her 17-year-old son. She was one of only three women on the 25-member US-appointed Governing Council until the transitional Iraqi government took over last June.
She then had a seat on a national council that oversaw the work of government and was elected to the National Assembly in January's elections.
Iraq said on Tuesday that a leading member of Saddam Hussein's government who was captured two years ago had been freed from custody by the former government because of poor health
Ghazi Hammud al-Ubaidi, one of the list of 55 former government leaders wanted by US authorities, was arrested soon after the fall of Saddam in April 2003.
He was freed recently by a US-appointed government committee headed by former prime minister Iyad Allawi, said Laith Kubba, a spokesman for Prime Minister Ibrahim al-Jaafari.
"Ghazi Hammud al-Ubaidi was freed by the former government," Kubba said, adding that the police have issued an arrest warrant for him.
Al-Ubaidi headed the Baath Party in Wassat province in central Iraq. He is believed to be the only figure so far released from those arrested on the list of 55.
Most of the high-level figures, including Saddam, have not been formally charged after months in US custody.