The killing of a Cardiff jihadist in Syria has been defended by a Welsh peer who was previously the independent reviewer of UK anti-terrorist laws.
Reyaad Khan, 21, died in Raqqa in August in the first targeted UK drone attack on a British citizen, Prime Minister David Cameron has confirmed.
Some MPs and Muslim leaders have questioned the legality of the killing.
Lord Carlile said it was a "relatively unusual" act but justified within international law.
Defence Secretary Michael Fallon has said the United Kingdom would "not hesitate" to launch more secret drone strikes in Syria to thwart potential terror plots.
He said the RAF strike was a "perfectly legal act of self defence".
David Cameron told MPs on Monday that Khan was targeted for planning "specific and barbaric attacks against the West".
Ruhul Amin, from Aberdeen, also died in the drone strike.
Former Welsh Liberal Democrat leader Lord Carlile, who was the Montgomeryshire MP from 1983 to 1997, told the BBC on Tuesday that there had been "no denial" from so-called Islamic State fighters "that Mr Khan and his colleagues did not intend to carry out the acts that the prime minister described".
"The overwhelming evidence is that they did, and therefore what occurred, albeit relatively unusual, was within international law," he said.
Muslim leaders in Cardiff have questioned the legality of the attack, and Cardiff Labour MPs Stephen Doughty and Kevin Brennan have asked for a meeting with the prime minister on the matter.
Mr Doughty, the member for Cardiff South and Penarth, said "as clear a case as possible" for the strike was needed.
Plaid Cymru's defence and foreign affairs spokesman, Hywel Williams, said the killing was "unprecedented" and called on Mr Cameron to explain the legal basis for the attack.
"It is deeply troubling that the Prime Minister has undermined the clear will of Parliament which voted against military strikes in Syria," he said.