UK Prime Minister David Cameron has vowed to do "whatever it takes" to protect the UK from extremists - and said he wants to work with technology companies to lock down loopholes which can be exploited by terrorist groups.
Speaking at an event in Colchester, Cameron said he had concerns over the way groups such as Islamic State might be able to communicate in future - and said more laws might be needed.
"My view is national security comes first. Whatever it takes, whatever is necessary to keep the British public safe, I will always be a Prime Minister who wants to push for those changes," he said.
"Over time, yes of course, we are going to do more to make sure that as technology develops we can make sure we can keep people safe," he added.
"I'm not satisfied that we can allow means of communication to develop which in extremis we are simply unable to intercept," Cameron said.