The gunmen, dressed as Iraqi soldiers, broke into the southeast Baghdad home of Sheikh Fadel Sarhid Ali around 4:00 am (0100 GMT) and killed the tribal leader, three of his sons and a son-in-law before escaping.
That attack was followed shortly afterwards by the assassination of a high ranking official in the ministry of industry, Radi Ismail Jawad, and the former chief of traffic police, General Mahdi Kassem, both in Baghdad.
Leaders from all religious and political affiliations have been regularly targeted by death squads in the strife following the fall of Saddam Hussein's regime in 2003.
The latest bloodshed came as the death toll from car bomb attack on Tuesday aimed at police on a busy market street in Kirkuk, northern Iraq, rose to 22, include four police. Twenty-eight people were wounded.
At a recent meeting of Iraqi factions in Cairo, the restoration of internal security and the buildup of the Iraqi army were given high priority along with calls for a timetable for the withdrawal of foreign troops.
Radical Shiite cleric, Moqtada Sadr, on Wednesday urged voters in
December's scheduled general election to back candidates who "call for the withdrawal of foreign forces," one of his spokesmen said.
Troop pullout
Meanwhile in televised remarks in Washington, US Secretary of State Condoleezza Rice said troop reductions could occur soon.
"The president has said that as soon as Iraqi forces are ready, we want to see a reduction in our own forces, and I think those days are going to be coming fairly soon when Iraqis are going to be more and more capable of carrying out the functions to secure their own future," Ms Rice told Fox News Channel.
About 159,000 US troops are currently deployed in Iraq ahead of the
December 15 general election, the final stage in the political transition to democracy after the fall of Saddam Hussein in April 2003.
Once the election is over, the number of US troops is expected to be
reduced to about 138,000, a figure US defence officials refer to as the "baseline."
Ms Rice insisted that for US troop withdrawal to begin, Iraqi security forces must demonstrate their ability to "hold territory" against the insurgency.
The remarks came amid increasing discussion over the presence of US-led foreign troops in the country, among Iraqis and by the US Congress.
A poll published on Tuesday showed that 63 percent of Americans favoured bringing troops home in the next year.
Another 61 percent doubted that democracy and stability could take hold in Iraq.
US authorities are eager to show a steady transfer of responsibility to the Iraqis, with regular announcements of successful joint military operations along with the handover of bases.
"The Iraqi Army has been the main effort in many of our operations," said Colonel John L Gronski of the US marines in Ramadi.
"They continue to exhibit professionalism and resolve in securing their country."
Iran visit
Iraqi government efforts to combat the insurgency took a new tack over the past two days with an offer by President Jalal Talabani, while in Cairo, to negotiate with insurgents.
He followed this up with a landmark visit to Iran that concluded with assurances from the Iranians to support Iraq's security.
"Iran is interested in our security just as it is interested in its own
security," Talabani said as he was seen off by hardline Iranian President Mahmoud Ahmadinejad.
"They all said one thing to me: that there are no limits to Iran's cooperation with and support for the Iraqi people and government."
Iran has often been accused of supporting insurgent attacks against US and British forces, a charge Iran denies.
Saddam trial
Meanwhile with Saddam's trial set to resume on Monday, sources close to the Iraqi High Tribunal said they believed his defence lawyers had suspended their boycott of proceedings and would attend the trial.
The defence team representing Saddam and seven former associates earlier this month vowed to stay away from the court to protest at the lack of adequate protection following the murder of two of their members.
Defence lawyers have been offered protection and the United States will take part in the investigation into the killings, according to one US official close to the tribunal.
"It is currently expected there will be at least one defence counsel for each defendant present at the trial on November 28," the official said.