MEXICO CITY (AFP) - Mexico has ordered an investigation into allegations the United States spied on both President Enrique Pena Nieto before his election and his predecessor Felipe Calderon, the interior minister said on Tuesday.

Interior Minister Miguel Angel Osorio Chong said he had asked the CISEN intelligence agency and federal police to conduct an "exhaustive" investigation to see whether such spying took place and whether any Mexican officials were complicit.

Mr Osorio Chong said the government has "revised and strengthened security mechanisms for the voice and data communications as well as the networks, software and encryption systems used by the president" since Pena Nieto took office in December.

Foreign Minister Jose Antonio Meade announced earlier that, once he returns from a trip to Geneva, he would summon the US ambassador to discuss the latest allegations.

Mr Meade urged the United States to include the allegations of spying on Calderon in a probe that President Barack Obama has pledged on previous claims that the National Security Agency spied on Pena Nieto.

The German weekly Der Spiegel, citing a secret document leaked by former NSA contractor Edward Snowden, reported that the spy agency snooped on Mr Calderon's emails from May 2010.

US journalist Glenn Greenwald, who gained access to Snowden's documents, had reported last month that the NSA gained access to Pena Nieto's emails when he was running for office last year.