US President Joe Biden has refused to answer reporters' questions about classified documents held by his private office for years.
Biden, flanked by his Secretary if State Antony Blinken, ignored shouted queries from journalists following a meeting in Mexico City with Mexican President Andres Manuel Lopez Obrador on Tuesday.
Staff interposed themselves in front of TV cameras and appeared to usher the media out of the room.
US TV news media reported on Monday that around 10 classified documents had been discovered by Biden's own lawyers at the Penn Biden Center for Diplomacy and Global Engagement. Attorney General Merrick Garland, who accompanied Biden on his Mexico trip, ordered a "review" of the documents.
The think-tank, based at the University of Pennsylvania, was officially founded by the former vice-president in 2018, although an official statement said: "The president periodically used this space from mid-2017 until the start of the 2020 campaign."
Critics pointed out that Biden was quick to condemn his predecessor Donald Trump after the FBI raided his Florida mansion on August 8 2022 — on Garland's orders — searching for official documents he took with him after leaving office. Trump insists he de-classified those files by presidential authority.
Newly-elected House of Representatives speaker Kevin McCarthy told reporters the revelation was "very concerning."
"He [Biden] has had these classified, and what has he said about the other president with classified documents?" McCarthy asked.