Two Iraqi security guards say they have been freed by kidnappers overnight but that the gunmen are still holding an American and a Nepali also seized from a villa used by a Saudi company in Baghdad.
There was no immediate claim of responsibility for yesterday's kidnapping.
The two Iraqis, initially described only as Arabs, returned to the villa after being freed during the night.
A third guard was killed when the gunmen attacked the villa in the affluent Mansour district of the Iraqi capital.
"They stormed the villa with automatic rifles and rocket-propelled grenades. They had no chance," said a policeman.
The American and Nepali work for the Saudi Arabian Trading and Contracting Company (Satco), a Riyadh-based company owned by Saudi and Lebanese businessmen that supplies US forces in Iraq, according to executives who know the firm.
At least 25 foreigners from a dozen countries, including Irish woman Ms Margaret Hassan, are thought to be held by kidnappers trying to drive US-led forces and foreign workers from Iraq.
Scores of foreigners have been abducted since April. Many have been freed but more than 35 have been killed, several of them beheaded.
The last two Americans to be kidnapped in Iraq were beheaded by a militant group led by al-Qaeda ally Abu Musab al-Zarqawi that demanded US-led forces free women detainees.
The two Americans, both construction contractors, were snatched from their home in Mansour, along with British engineer Ken Bigley, who was also decapitated.
The body and severed head of a Japanese backpacker kidnapped by Zarqawi's group was found on a Baghdad street on Saturday.
Three truckers, from Bangladesh, Sri Lanka and Somalia, were reported kidnapped last week. An Iraqi-Polish woman has also been seized in the last two weeks. Kidnappers have held two French journalists hostage since August.