No British citizen who has fought for so-called Islamic State should be allowed back into the country, the defence secretary has said.
In an interview with the Daily Mail, Gavin Williamson said: “Quite simply, my view is a dead terrorist can’t cause any harm to Britain.”
He said everything should be done “to destroy and eliminate that threat”.
At least 800 Britons have gone to Syria and Iraq to fight for IS and 130 of those have been killed in conflict.
Mr Williamson, who took over as defence secretary last month, told the newspaper: “I do not believe that any terrorist, whether they come from this country or any other, should ever be allowed back into this country.”
British fighters who had fled to other countries would also be found and stopped from returning to the UK, he said, adding that there would be no “safe space” abroad for them either.
“We have got to make sure that as (they) splinter and as they disperse across Iraq and Syria and other areas, we continue to hunt them down,” he said.
Mr Williamson’s predecessor Sir Michael Fallon said in October that British IS fighters in Syria and Iraq had made themselves “a legitimate target” who could end up on “the wrong end of an RAF or USAF missile”.
His comments came after it was reported that British IS recruiter Sally-Anne Jones had been killed in a US drone strike in Syria in June.
And Rory Stewart, the minister for international development, said the “only way” to deal with British IS fighters in Syria is “in almost every case” to kill them.
He said they can expect to be killed because of the “serious danger” they pose to the UK’s security.
In contrast, Max Hill QC, the Independent Reviewer of Terrorism Legislation, has said Britons who joined IS through “naivety” should be spared prosecution and instead be reintegrated into society if they return home.
Analysis: Can the UK legally kill jihadists?
By Dominic Casciani, BBC home affairs correspondent
Under British and international law, an aspiration to eliminate all known British IS recruits will take a little more consideration than simply launching a drone laden with fire-and-forget missiles.
In war, soldiers are immune from prosecution for murder. But the UK is not at war with the IS network – so the same immunity is not automatically available for counter-terrorism purposes.
There has to be some other legal basis for justifying the killing.
Two years ago, the government sent a three-paragraph letter to the United Nations Security Council setting out the case for killing Cardiff extremist Reyaad Khan.
That strike was legal under the “inherent right of self-defence”, it said, because the 21-year-old had been directing “imminent armed attacks”.
MPs have pushed for more information on the decision-making process, that some critics say could amount to an unreviewable secret power to launch “extra-judicial executions.”