Two local officials said some 150 militants early hours of Thursday carried out a coordinated operation during the night that included the highway killings, in the area of Sulaiman Bek, a town north of Baghdad.
The militants began by attacking the town itself with mortar rounds, rocket-propelled grenades and automatic weapons late on Wednesday.
That attack drew security forces away from the highway connecting Baghdad with north Iraq, after which a group of around 40 militants broke off and set up the checkpoint.
They only maintained it for about half an hour but were able to stop dozens of truck drivers, killing 14 execution-style who were Shias.
"These criminals belong to what is called the Islamic State of Iraq, and they targeted Shia drivers and left the Sunnis," local official Shalal Abdul Baban told AFP, referring to an al-Qaeda front group. "It was killing by ID," he said.
Iraqi identification cards list a person's name and place of birth, from which their religious affiliation can be surmised.
The entire operation including the attack on the town, in which at least one person was wounded, lasted for about three hours, after which the militants withdrew.
Sulaiman Bek was briefly seized by militants in late April, but the assailants later withdrew under a deal worked out by tribal leaders and government officials, allowing security forces to move back in.
The highway killings come just days after a highly-coordinated assault by militants on two Iraqi prisons that saw hundreds of inmates escape, an operation claimed by an al-Qaeda front group.
The militants attacked prisons in Abu Ghraib, west of Baghdad, and Taji, north of the capital, with mortar rounds, bombs and gunfire beginning on Sunday night, sparking clashes with security forces that lasted for 10 hours.
At least 500 prisoners, including senior al-Qaeda members, escaped during, while at least 20 security forces members and 21 prisoners died in the unrest.
INTERPOL said in an online statement on Wednesday that the escapes "constituted a major threat to global security" and that it had issued a regional security alert at Iraq's request.
BA/BA