Iraqi authorities say gunmen have killed three Syrian truck drivers on a main highway linking Baghdad to Syria and Jordan.

Police officials said that the gunmen stopped the trucks, killed the drivers, and burned the vehicles during the Sunday morning attack near Rutba town in far western Iraq.

The gunmen kidnapped also four Iraqis in the same area, according to the police.

A medical official in Rutba hospital confirmed receiving the three bodies. All officials spoke anonymously because they are not authorized to talk to media.

Both Iraqi Sunnis and Shiites have taken sides in Syria's war pitting mostly Sunni rebels against a regime dominated by a Shiite offshoot sect.

Iraqi security forces are struggling to contain the country's most relentless round of violence since the 2011 U.S. military withdrawal.