They appear to be the military forces of a fictional Arabic country and stage a coup against the country's president. In the introductory speech of the game is mentioned that the country was formerly a monarchy "colliding with the west", that would explain some of their western gear such as US helmets and British vests and gloves. However, it seems the country also had close ties with Russia as they are armed with old Soviet weaponry and equipment.
It seems that the OpFor was inspired by the Iraqi army and the various insurgencies during the Iraq War, but since the game was released in 2007 and the ongoing conflict was still a sensitive topic the developers made them a generic interpretation of the situation in the Middle East.
Generic three hole balaclava
Black PASGT helmet (6B7 helmet in MW Remastered)
A white/red colored keffiyeh wrapped in the "Spec Ops" method.