A civilian was “unintentionally” killed in an RAF airstrike on three Isis fighters in eastern Syria, the defence secretary has said.

In a written statement to parliament, Gavin Williamson said a civilian on a motorbike crossed into the strike area “at the least moment” before the blast on 26 March.

The death was “deeply regrettable”, the minister said.

It is the first time the Ministry of Defence has confirmed a civilian casualty during Britain’s campaign against the terror group in Iraq and Syria.

Three Isis fighters, who were driving in the Syrian Euphrates valley at the time, were also killed by the precision Hellfire missile, a statement from the MoD at the time reported.

The attack was carried out by an RAF Reaper drone, which had tracked the trio.

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The RAF has conducted over 1,600 strikes against Isis in Iraq and Syria as part of a US-led coalition, the defence secretary told parliament.

Mr Williamson said: “We do everything we can to minimise the risk to civilian life from UK strikes through our rigorous targeting processes and the professionalism of UK Service personnel.

“It is therefore deeply regrettable that a UK airstrike on 26 March 2018, targeting Daesh fighters in eastern Syria, resulted in an unintentional civilian fatality.

“During a strike to engage three Daesh fighters, a civilian motorbike crossed into the strike area at the last moment and it is assessed that one civilian was unintentionally killed."

Mr Williamson said the conclusion was reached through “post-strike analysis of all available evidence” and added that the US-led coalition against Isis would conduct its own investigation.

Syrian Democratic Forces take Raqqa from Isis – in pictures Show all 8 1 /8 Syrian Democratic Forces take Raqqa from Isis – in pictures Syrian Democratic Forces take Raqqa from Isis – in pictures Syrian Democratic Forces fighters celebrate victory in Raqqa atop of military vehicles REUTERS Syrian Democratic Forces take Raqqa from Isis – in pictures Fighters of Syrian Democratic Forces march past destroyed buildings as they celebrate victory REUTERS Syrian Democratic Forces take Raqqa from Isis – in pictures Fighters of Syrian Democratic Forces gesture the "V" sign in Raqqa REUTERS Syrian Democratic Forces take Raqqa from Isis – in pictures Fighters of Syrian Democratic Forces evacuate a civilian from the stadium REUTERS Syrian Democratic Forces take Raqqa from Isis – in pictures A civilian prays after she was rescued by fighters of Syrian Democratic Forces from the stadium REUTERS Syrian Democratic Forces take Raqqa from Isis – in pictures Syrian Democratic Forces fighters ride atop of military vehicles as they celebrate victory in Raqqa REUTERS Syrian Democratic Forces take Raqqa from Isis – in pictures Syrian Democratic Forces fighters celebrate victory in Raqqa REUTERS Syrian Democratic Forces take Raqqa from Isis – in pictures A fighter of Syrian Democratic Forces celebrates in Raqqa Reuters

Britain’s direct military involvement against Isis – also known as Daesh – is limited to the skies, but troops on the ground have been involved in training more than 60,000 members of the Iraqi security forces.

Intelligence, surveillance and reconnaissance has also been provided to coalition partners, according to Mr Williamson.

“These strikes are undertaken in the collective self-defence of Iraq as part of the global coalition to defeat Daesh, and at the request of the government of Iraq,” his statement said.

“As a result of the coalition’s action, Daesh has lost more than 98 per cent of the territory it once occupied in Iraq and Syria, and 7.7 million people have been liberated from its rule.”

He said such civilian deaths “remind us of the consequences of conflict and of the heavy price that the people of Syria have paid. It reminds us that when we undertake military action, we must do so knowing that it can never be completely without risk.

“Such incidents will not weaken our resolve to defeat Daesh and rid the world of its poisonous ideology of hate and intolerance.