German police have arrested a suspected Islamic State militant commander, who is believed to have pledged allegiance to Abū Bakr al-Baghdadi, near the city of Leipzig.

Bild reports that “Ahmad A. A.” was arrested with three others during a raid in Wachau, although the other detainees have since been released.

“The accused is strongly suspected of being a member of the foreign terrorist groups ‘Jabhat al-Nusra’ and ‘Islamic State’,” the federal prosecutor said.

According to his arrest warrant, Ahmad fought in Syria under the banner of the radical Islamist terror group Jabhat al-Nusra, an official franchise of al-Qaeda which has now gone solo and rebranded as Jabhat Fateh al-Sham.

The warrant alleges that Ahmad commanded one of al-Nusra’s fighting units as a so-called “emir” (head of a militia unit in a caliphate) in the Raqqa region, taking part in offensives which captured the cities of Dibsi Afnan and Tabka in November 2012 and February 2013.

However, when Abū Bakr al-Baghdadi’s Islamic State group – then also aligned with al-Qaeda – declared a merger between their organisations and al-Nusra, jihadists in Syria fell into dispute. Al-Nusra’s existing leadership denied the merger, obtaining a ruling from al-Qaeda leader Ayman al-Zawahiri in their favour, leading to clashes between loyalists of the previous leadership and fighters joining al-Baghdadi.

The Germans believe Ahmad pledged his allegiance to al-Baghdadi.

The Federal Prosecutor declined to say when he arrived in Germany or what they found in his flat, although it is possible he entered Europe posing as an asylum seeker after the Islamic State’s fortunes were reversed by an extensive Western bombing campaign, Russian-backed government offensives, and the resurgence of al-Nusra in rebel-held territory.

In June 2016, the then-director of the CIA, John Brennan, predicted that “as the pressure mounts on [Islamic State] we judge it will intensify its global terror campaign to maintain its dominance of the global terrorism agenda”, and that “infiltrating operatives into the West, including in refugee flows [and] smuggling routes” would be key to its strategy.