A German rapper turned Islamic State fighter notorious for holding a human head on camera has been killed fighting in Syria.

Denis Cuspert – known as Deso Dogg – was one of the so-called “gangsta jihadis” who travelled from European cities to join Isis after it declared a caliphate in Syria and Iraq.

Cuspert, 41, toured with the US rapper DMX in 2006 and was married briefly to an FBI translator assigned to monitor him.

He was killed on 17 January during clashes with anti-Isis forces in Deir ez-Zor province in eastern Syria.

Previous reports of his death proved unfounded but this time a pro-Isis media network released pictures of his bloodied corpse, SITE, a US-based consultancy that monitors extremist propaganda, reported.

Isis has lost almost all its territory in Syria and Iraq, continuing to hold only a few scattered villages and enclaves. Thousands of its foreign recruits and dozens of senior commanders have been killed.

The thousands of volunteer fighters who travelled from Europe to join Isis included many who had criminal backgrounds in their home countries.

Shiraz Maher, the deputy director of the International Centre for the Study of Radicalisation and Political Violence at King’s College London, said Isis had provided an opportunity to some individuals “to realise what they had been talking about”.

“There was this whole subculture that these guys were buying into: a macho world of clandestine behaviour beyond social norms … A lot of the appeal to these people was based on masculinity and bravado rather than something ideological or religious,” Maher said.

Cuspert had a German mother and Ghanaian father, and grew up in Berlin’s Kreuzberg district. He became involved in gangs, spent several years in young offenders’ institutions and was convicted of a series of minor offences.

As Deso Dogg, he recorded three albums which achieved moderate success, but ended his musical career in 2010. He converted to Islam in about 2007 but became interested in more radical strands of the faith after a serious car crash three years later. He left for Egypt in 2012 after falling under the influence of another convert and hardline preacher.

He reached Syria in about 2013, and was designated a global terrorist by the US state department in 2015. He appeared in a number of propaganda videos, including one in which he held up the head of an execution victim.

In June 2014, Cuspert married Daniela Greene, an FBI translator who had a “top secret” security clearance. Court testimony suggested the couple may have communicated privately via a secret Skype account. Greene told her FBI colleagues in Detroit she was going to Germany to see her parents but instead flew to Turkey, from where she travelled across the border to meet Cuspert in Syria.

“I really made a mess of things this time,” she told a friend in a July 2014 email from Isis territory, shortly before returning to the US and giving herself up to authorities.

Many high-profile attacks in Europe and the UK in recent years have involved extremists previously convicted for petty or serious crime.

Khalid Masood, the 52-year-old Briton who carried out the Westminster attack in London last year, had a string of criminal convictions. The attacker who killed 86 people in Nice in 2016 had been in trouble with the police for threatening behaviour, violence and petty theft. Several key members of the network that killed 140 in Paris in November 2015 had been involved in drug and arms sales.

Extremist recruitment efforts have specifically targeted former criminals, with one British group’s propaganda image of a fighter accompanied by the slogan: “Sometimes the people with the worst pasts create the best futures”.

Magnus Ranstorp, head of terrorism research at the Swedish Defence University, said the idea that religious extremist networks and criminal networks remained separate was wrong.

“People move in and out of each. Many who end up in gangs and extremism come from the same environments. There is an interesting crossover with music. A lot of gangs here in Sweden are doing their own music videos, with masked men and automatic weapons, just like the Isis videos,” he said.