'Senior Russian politicians have dismissed accusations by Theresa May that Moscow has meddled in elections and carried out cyber-espionage.
On Monday night, Mrs May accused Moscow of "planting fake stories" to "sow discord in the West".
She said Vladimir Putin's government was trying to "undermine free societies".
Russian senators accused the UK PM of "making a fool of herself" with a "counterproductive" speech.
But the top US diplomat in the UK, Woody Johnson, said countries engaging in such behaviour needed to be "called out".
President Donald Trump's newly appointed ambassador to the UK told BBC News that Mrs May "probably has evidence" of Russian meddling and she had "every right" to draw attention to it.'
Read More: Russian politicians dismiss PM's 'election meddling' claims