More drone strikes could be launched within weeks to kill terrorists in Syria plotting to wreak carnage in Britain, the Defence Secretary has indicated.
Michael Fallon said the Government would "not hesitate" to repeat the action that led to Britons being killed by an RAF drone in the Islamic State stronghold of Raqqah last month.
Prime Minister David Cameron revealed that jihadist Reyaad Khan, accused by the intelligence services of plotting "barbaric" attacks on "high-profile public commemorations" in the UK, was killed by a missile fired at his vehicle on August 21.
Mr Fallon defended the move and said the Government would use military strikes again if there was no other way to stop the terror cells.
He told BBC Radio 4's Today programme: "There are other terrorists involved in other plots that may come to fruition over the next few weeks and months and we wouldn't hesitate to take similar action again."
Mr Fallon refused to be drawn on the number of terrorists planning attacks against Britain but said it was more than three and revealed plots were also uncovered against Australia and the United States.
He said: "It's extremely dangerous because these are attacks that have been and are being planned against major public events on our streets. They are potentially attacks on members of our armed forces and on others, which would be extremely dangerous and would obviously involve the loss of life.
"Government has a duty, where it has information and the ability to prevent such attacks, government has a duty to deal with it."
The targeted killing of Khan sparked criticism of a "dangerous precedent" and warnings it will spark a legal challenge.
Fellow British citizen Ruhul Amin was one of two other IS fighters who died in the blast, which came three days before a US drone killed another alleged British plotter, Junaid Hussain.
Events presided over by the Queen - including one marking the 70th anniversary of VE Day in June - were reported to have been among the targets, but Downing Street said confirming details could disrupt ongoing prosecutions.
The Prime Minister said the targeting of Khan in Raqqah was justified on the grounds of "self-defence", as he and Hussain were actively involved in recruiting jihadists and orchestrating a number of plots.
Mr Fallon said the jihadis had been involved directly in plotting with people in Britain but would not confirm if any arrests had been made in the UK.
He told Today: "These were terrorists who'd been planning a series of attacks on the streets of our country, some involving public events, there are other terrorists making similar plans and we have to do what we can to keep our streets safe."
MPs rejected plans in 2013 for Britain to engage in military action in Syria against President Bashar Assad's regime but the move has hampered attempts to curb the spread of IS in the region.
Mr Fallon said the Government was prepared to take action against IS, also known as Isil, but a fresh vote on military action in Syria would need to be held in the Commons.
"At some point the new parliament will have to rethink the absurdity of us being able to strike against Isil in Iraq but not being able to strike Isil's command and control centres in north-east Syria," he told Today.
"To get parliamentary approval we have to be absolutely sure that we would win the vote, that we would establish a sufficient majority for it."