Mexican media, including the newspaper "El Universal," reported Tuesday that masked robbers armed with guns and knives intercepted the German tourists and their guides en route to the ruins at Palenque.

Villagers in the impoverished southern Mexican region, who sometimes demand small toll charges from visitors, had blocked the normal route.

Watch video 02:51 Saving an ancient Maya rainforest

Diverting onto a rural back-road, the tourists were initially given a police escort, but that ended at a regional boundary. The robbers then struck on a difficult stretch.

The robbers fled as another police squad arrived.

In the wake of the robbery, Chiapas state authorities pledged to tighten security along rural roads during the current Easter travel season.

The ruins set among jungle in the Palenque region comprise former palaces and temples and have been listed among UNESCO's world heritage sites since 1987.

Its growing number of visitors has reached 600,000, according to UNESCO.

ipj/rc (dpa, AP)