The revelation about the probe includes no details, but it promises to rekindle Republican rage about the Biden family, including Hunter Biden's business dealings and the elder Biden's anti-corruption push in Ukraine when he was US vice president.
Russian President Putin, who has praised President Donald Trump in the past for saying he wanted better ties with Moscow, has said Russia will work with any US leader, while noting what he called Joe Biden's "sharp anti-Russian rhetoric".
US Senator Josh Hawley shoots letters to Twitter's Jack Dorsey and Facebook's Mark Zuckerberg, asking them to testify at Senate sub-committee after social media giants blocked a news story about Democrat Joe Biden and his son Hunter Biden.