The troops were searching for former general Izzat Ibrahim al-Duri, who was officially number two to Saddam Hussein and apart from the ousted president is the highest ranking Iraqi on a US most-wanted list.
"There are reports that al-Douri is coordinating the attacks," said a US official in Washington on Wednesday, who spoke following a surge of attacks in Iraq.
It was unclear whether al-Duri directed the wave of car bombings, but US officials believe he is playing a key role in the resistance.
Al-Douri was vice chairman of the Revolutionary Command Council, commander of Iraq's northern region and deputy commander of the armed forces.
He has connections in Mosul through his daughter-in-law's family. Kurdish officials have also said he has an extensive network of contacts with former Iraqi military officers, including many from the Mosul region.
"If it is true that a tank was damaged to this sort of extent resulting in fatalities by a simple roadside bomb, depending on whatever size it was, that does not bode well for the future of the occupation"
Meanwhile, evidence that anti-US resistance attacks are growing more effective was provided when a heavily armoured Abrams tank was disabled for the first time by an explosive device.
The blast, announced on Wednesday, killed two soldiers in northern Iraq, a hotbed of anti-US resistance.
According to Pentagon figures, US toll is now higher since Washington declared an end to hostilities on 1 May than during the six-week main offensive before that.
Resistance attacks have killed 117 US soldiers since 1 May, against 114 during the invasion itself.
The attack on the Abrams tank came as officials warned that resistance forces striking at occupation troops were getting better organised with the help of foreign fighters, in an alliance thought to be coordinated by al-Duri.
The M1 Abrams weighs 69.5 tonnes and is the most heavily armoured battle tank to be used by the US troops.
"If it is true that a tank was damaged to this sort of extent resulting in fatalities by a simple roadside bomb, depending on whatever size it was, that does not bode well for the future of the occupation," said Patrick Garrett, an analyst with GlobalSecurity org, a private research group.
The past week has seen a surge of attacks, with an average of 33 daily attacks against occupation forces, up from 26 the previous week.