MEXICO CITY (Reuters) - A Mexican presidential candidate denounced on Tuesday alleged surveillance of his movements by the government and demanded an explanation, the latest in a series of accusations that Mexico is spying without due cause on its own citizens.

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Ricardo Anaya, a former congressman in second place in many opinion polls ahead of July’s election, published a video on Twitter that shows him confronting the driver of a vehicle following him on a highway who identifies himself as a member of the country’s main intelligence agency, CISEN.

In the video, the smiling agent says he is following Anaya “so that there’s no problem.”

Government surveillance has raised major concerns in Mexico in recent months, with reports of journalists, NGO workers and opposition politicians being tracked. Fears about Russian attempts to influence the election have also made headlines.

Anaya, who is a critic of the ruling Institutional Revolutionary Party (PRI) of President Enrique Pena Nieto and leads a left-right opposition coalition, also posted photos of another vehicle he claims was following him.

“Instead of following criminals, they spy on opponents of the government,” said Anaya, the former president of the conservative National Action Party (PAN), in a post on Twitter.

Anaya demanded in a statement that the government explain the criteria it uses to “spy on opposition politicians.”

A government official denied that Anaya was a surveillance target.

“This is not a case of espionage or spying on opponents or clandestine measures,” said Interior Minister Alfonso Navarrete at an event in Mexico City when asked about Anaya’s comments.

“We follow up on all important activities that happen in the country.”

Leftist presidential hopeful Andres Manuel Lopez Obrador, the front-runner in polls, said last week that he and his family have also been targets of spying.

Last year, the Pena Nieto government was criticized by United Nations human rights experts over University of Toronto research findings that it had targeted activists and journalists using sophisticated spying software known as Pegasus.

The software is marketed by Israeli company NSO Group, which only sells it to governments.

The researchers said they had found a trace of the Pegasus software in a phone belonging to a group of experts backed by the Inter-American Commission on Human Rights. The group had investigated the 2014 disappearance of 43 students that marked one of Mexico’s worst atrocities.