Internet-based companies should "show more responsibility" over extremist material and online methods for carrying out terror attacks, the head of counter-terrorism policing in Britain has said.
Metropolitan Police assistant commissioner Mark Rowley has repeated concerns made by politicians that terrorist material is too easily accessible online.
British Prime Minister Theresa May will meet French president Emmanuel Macron today as the two countries look to develop plans to create a new legal liability for tech companies failing to take action against unacceptable content on their platforms.
It comes after a series of deadly terror attacks in Westminster, Manchester and London Bridge.
Writing in the Times, Mr Rowley said: "We need communities to be more assertive at calling out extremists and radicalisers amongst us. It's not just overseas propaganda inspiring attacks.
"And we need communications and internet-based companies to show more responsibility.
"It is too easy for the angry, violent or vulnerable to access extremist views, learn about attack methodologies, conspire on encrypted applications and then acquire equipment to kill, all online."
Mr Rowley said "an internet going darker" was making it harder to look into people who may be of concern, but he welcomed the Prime Minister's efforts to look at strategies for dealing with extremism.