A Russian flag flies next to the US embassy building in Moscow on July 31, 2017. (MLADEN ANTONOV / AFP)

MOSCOW - Reports that Russian state hackers targeted one of US Democratic presidential candidate Joe Biden’s main election campaign advisory firms “look like nonsense”, Kremlin spokesman Dmitry Peskov told reporters on Thursday.

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Three people briefed on the matter told Reuters earlier that Microsoft Corp had alerted the firm in question that it had been targeted by suspected Russian state-backed hackers.

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The hacking attempts targeted staff at Washington-based SKDKnickerbocker, a campaign strategy and communications firm working with Biden and other prominent Democrats, over the past two months, the sources said.