Famous Machu Picchu in Peru. (David Nathan/QMI Agency)

The United States warned its citizens on Thursday to exercise caution in visiting Peru's famed Machu Picchu ruins through at least the end of the month and restricted State Department personnel from travelling there because of the threat of kidnappings.

The U.S. Embassy in Lima said it had information a criminal group could be planning to kidnap American tourists visiting Machu Picchu and the Cusco region where the ruins are tucked into the mountains, according to a statement.

Machu Picchu, which was built around the 1450s and was an important site during the Incan empire, draws hundreds of thousands of tourists to Peru every year.

Part of the Cusco region lies in a clutch of jungle valleys known as the VRAEM, where remaining members of the Maoist Shining Path insurgency have hidden out and now oversee cocaine trafficking.

Peru said on Wednesday it would start eradicating coca plants from farms in the VRAEM for the first time.

Last year, rebels kidnapped 36 Peruvian natural gas workers in La Convencion, Cusco, about 160 km from Machu Picchu. The hostages were later released unharmed.

The State Department did not mention the Shining Path or any political motives for potential kidnappings.