House Republicans have branded the first day of their impeachment inquiry against Joe Biden a success, saying they justified their case.

But expert witnesses called by Republicans cautioned there was not yet enough proof for impeachment.

Thursday's hearing was dominated by the business dealings of the president's son, Hunter, who Republicans allege was selling access to his father.

The White House has called the inquiry a "political stunt".

House Speaker Kevin McCarthy announced a formal impeachment inquiry in early September to look into allegations that Hunter Biden engaged in improper business dealings that benefited the president.

The formal inquiry granted lawmakers greater legal authority to investigate possible misconduct, after months of Republican probes failed to unearth any concrete evidence.

At the first hearing in the inquiry, it was Hunter Biden - not the president - who took up most of the Republican's oxygen.

Republican James Comer of Kentucky, chairman of the powerful Oversight Committee, said the panel would examine more than "two dozen pieces of evidence", including emails and bank records, which he said would reveal Joe Biden's "corruption and abuse of public office".

"At least 10 times, Joe Biden lied to the American people that he never spoke to his family about their business dealings," he said. "The American people demand accountability for this culture of corruption."

Mr Biden has previously said he "never" discussed business with his son.

Republicans on the committee, though, say Hunter Biden's former business partner Devon Archer told them during a closed-door hearing that Mr Biden had attended at least two dinners with his son's business associates.

But Mr Archer also testified that he had never heard business discussed during those encounters.

Chairman Comer and his colleagues also detailed a number of foreign payments to members of President Biden's family, including millions of dollars to Hunter Biden - suggesting the family was involved in a "pay to play" scheme.

One former business partner of Mr Biden had previously told House investigators the president's son was selling the "illusion of access" to his father.

Still, scepticism about the evidence was strong at the hearing, with a handful of spectators sporting white T-shirts printed with a photo of Chairman Comer and the words "NO EVIDENCE".

"If Republicans had a smoking gun or even a dripping water pistol they would be presenting it today," said Representative Jamie Raskin, the top-ranking Democrat on the committee. "But they've got nothing."

Hunter Biden's attorney, Abbe Lowell, in a statement on Thursday that: "once again Rep Comer peddles lies to support a premise - some wrongdoing by Hunter Biden or his family - that evaporates in thin air the moment facts come out".

Scepticism also came from an unlikely source - Republicans' expert witnesses.

Thursday's contentious hearing did not feature fact witnesses with direct knowledge about the Bidens. Instead, the panel heard from experts on tax law, criminal investigations and constitutional legal theory.

Two of the three conservative analysts called by Republicans to discuss Mr Biden's alleged wrongdoing told lawmakers they did not believe there was enough evidence to warrant impeachment.

"I am not here today to even suggest that there was corruption, fraud or wrongdoing," forensic accountant Bruce Dubinsky said. "More information needs to be gathered before I can make such an assessment."

Meanwhile, law professor Jonathan Turley told the panel "I do not believe that the current evidence would support articles of impeachment".

The sole expert witness called by the Democrats, Michael Gerhardt of the University of North Carolina, told lawmakers he had not seen credible proof to warrant the probe.

Calling the inquiry a "sham" and an "embarrassment", Democratic committee members sought to refocus the hearing on the looming shutdown and propped up a digital clock counting down to the Saturday deadline when the federal government will run out of money unless Congress reaches a budget deal.

"We're 62 hours away from shutting down the government of the United States of America and Republicans are launching an impeachment drive, based on a long debunked and discredited lie," Mr Raskin said.

The impeachment inquiry is expected to span weeks. It is too early to tell if congressional investigators will seek an impeachment vote in the full House of Representatives after holding hearings.

Separately, Hunter Biden has been criminally charged with three counts of lying when buying a firearm, after a proposed plea deal collapsed this past summer.