The only way of dealing with British Islamic State fighters in Syria will be to kill them in almost every case, an international development minister has said.
Rory Stewart said converts to the terror group believed in an "extremely hateful doctrine", saying fighters can expect to be killed given the threat they pose to British security.
Hundreds of British citizens are known to have travelled to Syria to fight with Islamist groups during the course of the six-year conflict.
Brett McGurk, a top US envoy for the coalition fighting Islamic State (IS), has said his mission is to ensure every foreign IS fighter in Syria dies in Syria.
Mr Stewart was asked about the comments on BBC Radio 5 Live's Pienaar's Politics.
The minister said they were "very difficult moral issues", adding: "These are people who have essentially moved away from any kind of allegiance towards the British Government.
"They are absolutely dedicated, as members of the Islamic State, towards the creation of a caliphate, they believe in an extremely hateful doctrine which involves killing themselves, killing others and trying to use violence and brutality to create an eighth century, or seventh century, state.
"So I'm afraid we have to be serious about the fact these people are a serious danger to us, and unfortunately the only way of dealing with them will be, in almost every case, to kill them."
Mr Stewart, a former diplomat, went on to say: "These are people who are executing people in the back of their heads, who have held women and children hostage, who are torturing and murdering trying by violence to impose their will.
"Our response has to be, when somebody does that, I'm afraid, to deal with that."
Mr Stewart also said British authorities had made it "very clear" that people should not be volunteering with militia groups to fight IS.
"If you wish to serve your country and you wish to fight terrorism, then please apply to join the military or join the police or join our intelligence services, we'll train you, we'll work with you to do it in a legal and controlled fashion," he said.
Mr Stewart also confirmed it remained British policy to remove Syrian president Bashar Assad.
"I don't think anyone should be in any doubt that the control that he has is brutal and ultimately fragile," said Mr Stewart.
"The policy of the British Government is that Bashar al-Assad needs to step aside and we need transition to a new government, because so long as that man is in power it is going to be impossible to have a long-term, stable, sustainable future for Syria."
£10m aid package for innocent Raqqa citizens
Britain has announced a £10 million aid package to end the "death sentence" innocent people in the liberated Syrian city of Raqqa still face from Islamic State (IS) booby-traps and war wounds.
The city, described by the Government as "the head of the snake" of the so-called caliphate claimed by IS, was formally liberated on Friday when Syrian Democratic Forces, a group of militia factions, declared victory over the terror group.
But International Development Secretary Priti Patel called on the international community to follow the UK in helping the hundreds of thousands who were forced to leave with nothing and are suffering life-threatening injuries and trauma after years of violence, bombing and landmines planted across the city.
Others have been held hostage by IS, also known as Daesh, or forced into hiding within the city itself.
The UK money will help clear landmines and restock hospitals so displaced Syrians can eventually return home and those in the city can rebuild their lives.