Gunmen wearing Iraqi police uniforms have raided the offices of a security firm in Baghdad, seizing 50 employees.
Among those captured is the head of the private Al Rawafed firm.
The incident came after the bodies of 20 men were found dumped in the Iraqi capital.
18 were left strangled or shot in a minibus in a mainly Sunni populated district of west Baghdad. Two were found in east Baghdad tied up and shot.
Rumsfeld accuses media
Earlier, the US Defence Secretary, Donald Rumsfeld, accused the media of overstating the severity of recent sectarian violence in Iraq.
Mr Rumsfeld said he did not believe a civil war was going on in Iraq, although he admitted that such a danger remained.
He said that his generals had downplayed the recent violence between Sunni and Shias and accused journalists of exaggerating the situation.