The incident occurred at 6.30am (0330 GMT) on Thursday, when armed men opened fire on a minibus that had gone to pick up the businessman from the Bakhan hotel, killing all six on board, police Lieutenant Bassam al-Abid said.
The Turkish businessman, identified as Abdulkadir Tanrikulu, was captured by at least 10 men.
The pavement was blood stained in front of the hotel.
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 added.
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 with US-led forces have frequently been targeted.
Many have been captured in Iraq over the past year. Some have been released - often following payment of ransoms - but many have been killed by fighters.
Al-Sistani aides assassinated
Also on Thursday, armed men 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 2km south of Baghdad, along with his son and four guards.
Another aide working in Sistani's office in Najaf was also found dead.
Iraqi officials have not confirmed the reports.