Seven Iraqi workers with a construction company have been killed in the southern city of Basra, police say.
Iraqi woman mourns the destruction of a Shia shrine near Baquba
Ten employees were handcuffed and blindfolded and taken to a residential area in the northern part of the city.
They were lined up against a wall to be shot. Seven of them were killed, but three managed to escape.
Separately, two policemen were killed when a large convoy transporting police vehicles was ambushed by gunmen near Baghdad, police have said.
Eighteen others were injured in the attack, which took place late on Thursday when the convoy deviated from their planned route while returning to the southern city of Najaf.
Thirty-five police made their way back to Najaf and another 53 headed to one of Baghdad's main police stations.
The convoy from Najaf had gone to Taji, near Baghdad, to receive new vehicles.
In other violence in Iraq:
- Two US marines are killed and 22 wounded in fighting in western Anbar province on Thursday, the US military says
- At least four people die in separate bomb attacks on two Sunni mosques in Baquba. The attacks came as worshippers left the mosques after midday Friday prayers
- Two Iraqis are killed and four British servicemen wounded when a British military convoy is attacked by a suicide car bomber in Basra on Friday
- A suicide bomber attacks a police station in the northern city of Mosul, wounding six people, including five policemen.
The victims of the attack on the construction company in Basra were all Sunni Arabs according to a police source.
The fact that Basra and the surrounding region is overwhelmingly Shia is bound to lead to concerns that this is another sectarian attack, BBC Baghdad correspondent Andrew North says.
This kind of violence and intimidation has led almost 11,000 families, both Sunni and Shia, to flee their homes, according to Iraqi government figures.
The UN's deputy humanitarian co-ordinator in Iraq, Yacoub El Hillo, told the BBC the situation is becoming evermore serious, and without political intervention, the numbers of displaced people will keep rising.
The security situation, he said, was making it much harder to get humanitarian supplies to displaced people.
With the increase in numbers, "the situation is reaching a critical point now in terms of resources", Mr Hillo said.
US MILITARY ASSESSMENT OF STABILITY IN IRAQ
Ratings based on governance, security and economic situations
Stable: Fully-functioning government; strong economic development; local security forces maintain rule of law
Moderate: Government functions, but with some concerns; economy developing slowly, with unemployment problems; security under control but with potential for instability
Serious: Government not fully formed; economy stagnant; unemployment high; routine anti-Iraq forces activity, assassinations and extremism
Critical: Government not functioning or only single strong leader; no infrastructure for economy to develop; high levels of anti-Iraq forces activity, assassinations and extremism
Assessment made in January 2006. Sectarian violence in Iraq has surged since February