Multiple US media reports say more classified documents from the period when President Joe Biden was vice president have been found at a new location.

NBC TV and other outlets report that Biden's aides found more classified documents in a separate location, but the number is not known.

A batch of classified documents from Biden's vice presidency were discovered last November at his private office in Washington.

Biden has said he was surprised by the discovery, and his team is cooperating with a review into why they were there.

Biden did not make the first discovery public until it was reported by the media.

Republicans are stepping up criticism of Biden's handling of the matter, as he has pointed to careless management of classified documents after they were found at the home of former President Donald Trump.