A computer expert and businessman from Cardiff who became one of Islamic State's (Isis) top hackers has been killed by a US drone strike. Although born in Bangladesh, Siful Haque Sujan, 31, had lived in the UK since 2003 and had studied computer system engineering at the University of Glamorgan and set up a number of businesses in Wales.

The Pentagon said that Sujan, a senior Daesh (Islamic State) leader, was killed in a drone strike in the self-declared capital of the caliphate – Raqqa on 10 December.

Sujan replaced another Briton with expert cyber skills, Junaid Hussain, who was killed by an air strike in August, and was also a leading figure in the IS hacking campaign and creating cyber defences against Western spies. Hussain had been credited with creating an outreach programme tempting foreign fighters from Europe and elsewhere to the IS frontline in Syria and Iraq.

Washington believes that Hussain was in contact with two men who attacked a "Draw a Cartoon of the Prophet" event in Texas in May. And Sujan, who renamed himself Abu Khalid al-Bengali was implicated in "external operations" by the US military which may have been the extension of the infamous IS outreach project.

Sujan arrived in the UK in 2003 and set up a computer firm providing online ordering systems in Newport. But after the death of a family member he became increasingly attached to religion.

Despite fighting to stay in the UK at an immigration tribunal in 2014 within a year he had left to join IS telling his friends that he and his wife wanted to return to Bangladesh - but within 18 months of his arrival in Syria he was dead.

One of his business associates, who had known him for more than 10 years, told The Telegraph: "He was an entrepreneur and he became a friend. He helped everyone create websites for their businesses.

"He was always coming up with ideas. He was very intelligent and persistent but was just a normal run of the mill chap. He loved helping people and was friends with everybody and it didn't matter about their religion or culture."