LIMA, Dec 30 (Reuters) - A train driver was killed and 40 more people were injured on Tuesday after two trains collided head-on on the railway leading to the Inca citadel of Machu Picchu, the Andean nation's top tourist site that draws well over 1 million visitors each year.

Police are investigating the collision between trains operated by Inca Rail S.A. and PeruRail S.A., which mainly transport tourists to the iconic site. A health official said about 20 people were in relatively serious condition.

A police officer added that foreign tourists were among the injured.

Images posted on social media shortly after the crash showed the badly damaged locomotives facing each other on the track, broken glass strewn around and injured people being treated on the sides of the tracks.

(Reporting by Marco Aquino; Editing by Stephen Coates)