In Baghdad, armed men stopped a minibus and killed all eight people aboard, while a roadside bomb in the capital exploded near a police patrol, killing five Iraqis and wounding nine on Thursday.
Police 1st Lieutenant Haitham Abd al-Razaq said those killed in the minibus attack were car mechanics heading to work and their driver. The gunmen ordered them off the bus in a remote area of southwestern Baghdad and shot them, he said.
Meanwhile Des Browne, the British defence secretary, met soldiers in Basra in what aides described as an attempt to "understand the situation better".
British troops are facing the
wrath of Iraqis in Basra
A British official in Basra, where recent attacks on British troops and disputes among local leaders have caused concern, said: "He's here to learn.
"He's here to meet as many of the people on the ground as possible and learn about the situation."
Browne, who took on the job in a cabinet reshuffle two weeks ago, is accompanied by Air Chief Marshall Jock Stirrup, the chief of the defence staff.
Britain has 8,000 soldiers in Iraq.
Before briefings from commanders on arrival, Browne said Basra, Iraq's second city, was under control despite the death of seven soldiers in the area this month.
Five British soldiers were killed in a helicopter crash on May 6, and two were killed by a roadside bomb a week later.
After the helicopter came down, hit by a rocket according to police, troops clashed with rioters at the scene in the worst violence in the southern Iraqi city since the fall of Saddam Hussein in 2003.
Up to five Iraqis are believed to have died.
It was also reported on Thursday that 15 tae kwon do players had been kidnapped on Wednesday on a road between the cities of Falluja and Ramadi. The athletes were members of a private sports club with hopes to one day compete at the Olympics.
Jamal Abd al-Karim, an official with the Iraqi Olympic Committee, which oversees professional and amateur sports teams, said: "We are negotiating with the kidnappers who are demanding $100,000 in ransom. We are doing our best to ensure their release."
US-led forces said they killed three fighters and wounded 10 more in two separate gun battles on Wednesday in Mosul, 360km northwest of Baghdad.