evidence: Hunter Biden, second son of US President Joe Biden, is being investigated by the Justice Department over his finances including, according to US media reports, some of his business dealings in China. [...] Asked about the allegations, Joe Biden told a reporter it was a "smear campaign". No criminal activity has been proven, and no evidence has emerged that Mr Biden did anything to intentionally benefit his son. [...] Donald Trump and his allies accused Joe Biden of wrongdoing because he had pushed, while vice-president, for the Ukrainian government to fire its top prosecutor, who was investigating the company for which Hunter worked.