Facebook CEO Mark Zuckerberg has told US Senators his company is in a constant battle with Russian operators seeking to exploit the social network.

“This is an arms race. They’re going to keep getting better,” he said.

Facebook CEO Mark Zuckerberg

Mr Zuckerberg was answering questions in the wake of the Cambridge Analytica data collection scandal.

He also revealed Robert Mueller, the special counsel investigating alleged Russian meddling in the 2016 election, had interviewed Facebook staff.

Zuckerberg said that Facebook has been served with subpoenas by special counsel Mueller’s office but then backs off and said that Facebook is “working with them”, including meetings.

Mr Zuckerberg said he has not been among those interviewed by Mr Mueller’s office.

But he added: “Our work with the special counsel is confidential and I want to make sure that in an open session I’m not revealing something that’s confidential”.

Asked about Facebook’s role in the allegation against Russia, Mr Zuckerberg said the company was developing new tools to identify fake accounts.

The Facebook CEO was appearing in front of a joint session of several US senate committees, after it was revealed in recent weeks that about 87 million people had their profile information accessed by marketing firm Cambridge Analytica.

Cambridge Analytica is best known for its association with Donald Trump’s 2016 election campaign, and has claimed it played “an integral part” in Mr Trump’s victory.

But it says none of the data involved in the recent scandal was used to help the Trump campaign.