Former U.S. Defense Secretary Robert Gates -- Burning Body Photos Should Be Investigated

Former Secretary of Defense Robert Gates thinks the Pentagon and the Marine Corps are doing the right thing by investigating the graphic photos showing Marines who are burning the bodies of what appear to be Iraqi insurgents.

TMZ broke the story ... we obtained 41 pics -- some way too graphic to post -- which show marines pouring gasoline or some other flammable on 2 bodies and then lighting them on fire. There's another pic of a marine mugging for the camera next to a body, and another showing a U.S. soldier riffling through the pocket of a body.

The Marine Corp has launched a formal investigation and the Pentagon told TMZ they're taking it seriously because it's a military crime to mishandle bodies.

BTW ... Gates is in a cervical neck brace -- he fell at his home on New Year's Day and fractured his first vertebrae.