A British volunteer has been killed fighting against Isis alongside US-backed militias in Syria as an offensive to retake the group’s de-facto capital intensifies.

The Kurdish People’s Protection Units (YPG) hailed Luke Rutter as a “martyr”, saying he died during battles in Raqqa on 5 July.

In a video recorded after the 22-year-old formally enlisted in March, Mr Rutter said he joined the YPG because it “stands for the best opportunity for peace in the region”.

“I lied to people I care about to come here. I said that I was going somewhere else,” he added.

“I apologise massively for that. Apart from that I don’t regret my decision and I hope that you respect it.”

Footage posted online by the YPG showed Mr Rutter sitting in Syria wearing combat fatigues with a gun slung across his lap.

Luke Rutter, 22, was killed fighting with the YPG against Isis in Raqqa on 5 July 2017 (YPG)

He said he had taken the Kurdish name Soro Zinar, a practice undertaken by all foreign fighters, and was born in Birkenhead, Merseyside.

Mr Rutter described his education as “nothing very significant” before he attended one of the YPG’s camps, including training in combat, the Kurdish language and the force’s ideology.

Commanders said Mr Rutter was “martyred in the fight against Daesh fascism in Raqqa on 5 July”.

A Kurdish activist said they had told Mr Rutter’s mother, Caroline, of her son’s death on Saturday, telling The Guardian: “She was obviously very upset. She said she didn’t know he was even in Syria.”

A YPG source told The Guardian he was part of a foot patrol that came under heavy grenade and gunfire from Isis after a fighter stepped on one of the countless mines laid in Raqqa’s streets.

Two American volunteers, 28-year-old Robert Grodt and Nicholas Warden, 29, were also named among those killed.

Mr Grodt was previously known for his activism with Occupy Wall Street in 2012 and had a young child with his partner.

“Comrades Demhat, Rodi and Soro, like all their other comrades, joined the fight to end Daesh [Isis] barbarity and sacrificed themselves for a common and free life for all peoples,” said the YPG, using the trio’s Kurdish names.

Kimberley Taylor, 27, left the UK in March 2016 and joined the Women's Protection Units (YPJ) in Syria (Facebook)

The force gave the date of Mr Rutter and Mr Warden’s deaths as 5 July, and Mr Grodt as the following day.

Mr Rutter is believed to be the fourth British volunteer killed so far while battling Isis alongside the YPG, while several British citizens remain on front lines.

Among them is the UK’s only known female volunteer, Kimberley Taylor, and members of the International Freedom Battalion.

Ms Taylor, who posted a tribute to Mr Rutter on her Facebook page on Tuesday, told The Independent she was preparing for a “bloodbath” in Raqqa earlier this year, while British members of a group formerly known as the Bob Crow Brigade said “dying for socialism is an honour”.

Ryan Lock, 20, a former chef from Chichester, West Sussex, shot himself to avoid falling captive to Isis in December, while 22-year-old Dean Evans, 22, a dairy farmer from Reading, died in the city of Manbij last July.

Konstandinos Erik Scurfield, a 25-year-old former Royal Marine from Barnsley, South Yorkshire, died in the northern village of Tel Khuzela in March 2015.

They are among dozens of foreign volunteers including men from Australia, Germany and the US killed while fighting for the YPG.

Ryan Lock died on 21 December, two months before he intended to return to the UK (Facebook)

It is part of the Syrian Democratic Forces alliance (SDF) being backed by the US to drive Isis out of its de-facto capital of Raqqa.

Fighters are receiving weapons, air cover, logistics and special forces support from members of the US-led coalition as the advance into the densely populated city continues.

The West’s backing has angered Turkey, which regards the YPG and other Kurdish factions as terrorists and launched an offensive using rival Syrian rebels to drive the group and Isis militants back from its border last year.

At least 850 people are known to have travelled from the UK to join jihadi groups in Syria and Iraq, with about half believed to have returned and an unconfirmed number being killed.

The government has not confirmed the number of British volunteers fighting with anti-Isis groups, but warned that “anyone who does travel to Syria, for whatever reason, is putting themselves in considerable danger”.

Anyone returning to the UK after volunteering with the YPG also faces the threat of prosecution for offences including murder and terrorism, although their treatment has so far been inconsistent.