President Joe Biden on Thursday downplayed the furor over the discovery of old classified documents improperly stored in his personal belongings, saying "there's nothing there."

Asked by reporters during a trip to California about the issue, he said: "I think you're going to find there's nothing there."

"I have no regrets. I'm following what the lawyers have told me they want me to do. It's exactly what we're doing. There's no there there."

Biden's defiant comments came just over a week after news first emerged that around a dozen secret documents dating from his time as vice president to Barack Obama had been found sitting in a former Biden office space. A handful more documents were subsequently discovered in the garage and home of the president in Delaware.

The uproar has engulfed the White House and threatened to overshadow what allies expect to be the Democrat's announcement in the near future that he's seeking a second term in the 2024 election.

Although the case is far less serious than Republican Donald Trump's hauling off of hundreds of documents from the White House to his Florida residence after leaving office, Biden is under severe pressure from the media, Republicans in Congress and a Justice Department probe run by a special counsel.

After days of the White House going on the defensive and refusing to answer reporters' questions, Biden sought to strike back, insisting that he is acting properly in a situation that the White House argues was nothing more than an accidental misplacing of the materials.

"Look," Biden said, after initially showing displeasure that reporters raised the question while he was in California to show support for victims of massive flooding and weather damage.

"We found a handful of documents... were filed in the wrong place. We immediately turned them over to the Archives and the Justice Department. We're fully cooperating and looking forward to getting this resolved quickly," he said.

Politically explosive

The issue, which first came to light in a CBS News report on January 9, caught the White House badly off guard, denting Biden's brand as a return to competency and honesty after the scandal-filled Trump years.

In addition to tarnishing Biden, the appointment of a special counsel to oversee the Justice Department investigation into his handling of the vice presidential documents is widely seen as weakening the ongoing probe by a different special counsel into Trump's case.

Trump, who is himself seeking a second term in 2024, repeatedly refused to cooperate with the authorities trying to retrieve his far bigger haul of classified documents. However, prosecution of the Republican would now seem less likely, with the Justice Department possibly wishing to avoid seeming to treat Trump more harshly in what is already a politically explosive situation.

Congressional Republicans, who took control of the US House of Representatives this month -- with far-right conservatives holding the balance of power -- have already promised fierce probes of their own.

On Tuesday, the White House accused Republicans of "faking outrage" over Biden's documents.