US Election debate: Donald Trump attacks Joe Biden's son Hunter over cocaine use, business activity

US President Donald Trump took repeated swipes at Democrat Joe Biden's family during the first Presidential debate on Wednesday.

The pair had multiple heated exchanges as they tried to win over voters ahead of the US election, which is being held on November 3.

Trump launched into an attack on Biden's son Hunter about his business activities and past drug use. Trump said Hunter was "thrown out" of the military for cocaine use, which Biden said wasn't true.

"He didn't have a job until you became vice president. Once you became vice president, he made a fortune in Ukraine, in China, in Moscow, in various other places," Trump said.

He was referring to Hunter's former job when he served on the board of Burisma Holdings, a major Ukrainian natural gas company, from 2014 to 2019. It's also alleged Hunter leveraged his father's position as vice president to get control in business dealings.

"That is simply not true," Biden responded. "My son, like a lot of people that we know at home, had a drug problem. He's overtaken it, he's fixed it, he's worked on it and I'm proud of him."

Biden repeatedly said his son wasn't given "tens of millions of dollars" as Trump alleged, saying that's been "totally discredited".

As the debate continued to heighten, Trump went on to say Hunter received $3.5 million from the mayor of Moscow's wife, questioning, "What did he do to deserve that?"

Earlier in September, the Senate Homeland Security and Finance committees released a report into an investigation into Hunter's work at Burisma. The report said officials within the Obama administration "ignored the glaring warning signs when the vice president's son joined the board of a company owned by a corrupt Ukrainian oligarch".

The report also included a claim that Hunter "received $3.5 million in a wire transfer" from Elena Baturina, wife of the former mayor of Moscow.

"None of that is true. It's totally discredited," Biden said.

"Did they pay him $183,000 a month with no experience in energy?" Trump asked.

Biden said his son "did nothing wrong" while working at Burisma.

Debate moderator Chris Wallace then stepped in to try and get the discussion back on course and told Trump to let Biden answer.

"He won't let me answer because he knows I have the truth," Biden said.

"His position has been totally, thoroughly discredited by the media, by our allies, by the World Bank, by everyone. As a matter of fact, even the people that testify under oath in his administration said I did my job and I did it very well."

When Wallace said Biden can get the final word in that section of the debate, the former vice president said "it's hard to get any word in with this clown".

"Here's the deal. We want to talk about families and ethics - I don't want to do that. His family we could talk about all night," Biden said.

In a post-debate analysis, CNN chief political correspondent Dana Bash said Biden could've used Trump's attacks to his advantage.

"That was a moment where Joe Biden was able to shine when the President was incredibly low."