Russia is still interfering in US politics, according to FBI director Christopher Wray.
He was answering questions about online disinformation at a US House judiciary committee hearing.
"We are seeing, and have never stopped seeing, efforts to engage in malign foreign influence by the Russians," he told lawmakers.
China is also using disinformation campaigns to shift government policy and public opinion, he said.
"Other countries, like China for example, have very active foreign malign influence efforts in this country," he said.
"In their instance, it's more geared towards trying to shift our policy and our public opinion to be pro-China on a variety of issues."
Mr Wray told politicians that Russia's use of social media to spread disinformation had "never stopped" but added that it was not currently on the same scale as seen during the 2016 presidential election campaign.
As part of special counsel Robert Mueller's investigation into Russian interference in the presidential election, 13 people who worked for Russia's Internet Research Agency (IRA) were charged with trying to undermine the election.
The former FBI director spent two years looking into alleged collusion between the 2016 Trump campaign and Russia and concluded that Russia had interfered in the election with the intention of benefitting Mr Trump's campaign. But he found no evidence of a conspiracy.
During his testimony, Mr Wray warned that other "adversary nations" were now considering adopting similar disinformation tactics to those used by Russia.
Facebook has actively removed accounts allegedly involved in spreading fake news.
And in 2018 Twitter highlighted more than 10 million tweets posted by suspected state-backed Russian and Iranian actors, in order to aid studies into how its platform had been used to try to influence the public.