At 6.30am (0330 GMT) on Thursday, armed men opened fire on a minibus that had gone to pick up a Turkish businessman from the Bakhan Hotel in central Baghdad.
All six on board were killed, police Lieutenant Bassam al-Abid said.
The businessman, identified as Abdulkadir Tanrikulu, was captured by at least 10 men.
Five of the dead were local Iraqi employees working for the businessman, who runs a construction company, al-Abid said. The other victim was the driver of the minibus.
The assailants carried the bodies off the bus and drove off in the vehicle and two other cars, al-Abid said.
A Turkish news channel said the construction company was working in Iraq with the US.
An employee of the hotel, who gave only his first name, Alaa, said the businessman has been in Iraq for about a year.
Iraqis and foreigners working for
US forces are a favoured target
Elsewhere, an Egyptian was seized around the northern Iraqi city of Kirkuk, local police and party officials said on Thursday.
"Egyptian Abd al-Khalik Ahmad, 43, who worked at a service station, was kidnapped on Thursday in front of his workplace by armed men who arrived in two cars, some of whom wore uniforms of the New Iraqi Army," Lieutenant-Colonel Ali Ahmad said.
In a separate development on Thursday, armed men stole millions of dollars worth of Iraqi dinars after breaking into a bank in Ramadi, the troubled capital of western Anbar province.
Two aides of Ayat Allah al-Sistani
have been found dead this week
The men broke into Al-Rashid Bank and stole $13.5 million worth of Iraqi dinars.
"At 11am (0800 GMT), a group broke into the Al-Rashid Bank and locked all the employees in a room and took all the money from the bank before escaping," a police captain said.
Against this backdrop of continued unrest, it was revealed on Thursday that armed men have killed two aides to Shia cleric Grand Ayat Allah Ali al-Sistani, a senior official working with him said.
Cleric Mahmud al-Madahaini was killed on Wednesday in Salman Pak, an ancient town two kilometres south of Baghdad, along with his son and four guards. Halim al-Afghani, another aide working in Sistani's office in Najaf, was also found dead.
Iraqi officials have not confirmed the reports.
Elsewhere too, there has been no let-up in violence. In the city of Hyit west of Ramadi, two US military vehicles were destroyed in a rocket attack on Thursday, Aljazeera reported. US helicopters were seen evacuating wounded US soldiers.
And in the Haqlaniya area, west of Ramadi, an explosive device went off near a US military patrol, destroying two military vehicles.
Aljazeera also reported that US forces have detained Shaikh Ahmad al-Jiburi, a member of the Association of Muslim Scholars and imam of Al-Khashab Mosque in al-Huriya neighbourhood, northwest of Baghdad
The raid damaged his house and the mosque.
Furthermore, in the Buhriz neighbourhood, south of Baquba, Imad Majid, a member of the Iraqi Communist Party, was shot dead by armed men.
While in al-Aziziya, south of Baghdad, four Iraqi police officers were wounded in an attack targeting their patrol.