An unnamed group said in a statement left near the bodies that the drivers were Jordanian and had delivered supplies to US forces at Ain al-Asad military base near Haditha city, west of Ramadi, Aljazeera learned.
In November, Iraqi kidnappers freed three Jordanian truck drivers they had abducted. The three men had appeared on a video tape during their captivity, urging their government to tell Jordanians not to work with US-led forces in Iraq.
A fourth Jordanian driver, who was in a convoy with the three abducted ones, was killed during their capture, officials said.
Fighters in Iraq have seized scores of foreigners as part of a campaign to try to drive foreign companies and workers out of the country.
Meanwhile, a journalist for the French daily Liberation has gone missing in Baghdad along with her Iraqi translator.
Journalist Florence Aubenas has
been missing for over 24 hours
"We have had no news from Florence Aubenas in over 24 hours, nor of her assistant, Husayn Hanun al-Saadi," the Paris-based paper said.
Aubenas and al-Saadi left their Baghdad hotel early on Wednesday but have not returned nor been seen since.
The development triggered immediate concerns in France for their well-being, with the foreign ministry saying "every effort is being made by our representatives in Baghdad and by the ministry in Paris to find them".
Two French reporters, Georges Malbrunot of Le Figaro newspaper and Christian Chesnot of Radio France Internationale, were released by fighters in Iraq on 12 December after being held hostage for four months.