During a regular daily news briefing, in which he usually expounds on everything from history and economics to culture, Lopez Obrador said the device had been found in a room used for meetings in the National Palace, his headquarters.

"Just imagine, they've been recording us in a meeting room, here in the Palace," the president said as he reflected on the importance of free speech and transparency.

Lopez Obrador, who didn't provide details on the camera or how it came to be there, said he had no secrets.

"What we talk about is completely legal, transparent, and there's nothing that could be used against us," he said.

During the presidential campaign last year, Lopez Obrador said he and his family were the victims of spying. Upon taking office in December, he put an end to the former national intelligence agency CISEN, giving the body a new name.

Lopez Obrador has accused previous governments of lacking transparency and suppressing dissent. He frequently blames negative reports about his administration on efforts by unnamed "adversaries" and "conservatives" to thwart his agenda.

The administration of his predecessor, Enrique Pena Nieto, faced persistent criticism over alleged surveillance by the state, and numerous reports were published of journalists, NGO workers and opposition politicians being snooped upon.