British police have arrested four terrorism suspects as part of an Italian-led European operation against alleged members of a jihadi network affiliated to al-Qaeda. The four men aged 33, 38, 52 and 38 were held on 12 November in separate raids in Derby, Hull, Sheffield and Birmingham, the North East Counter Terrorism unit said.

They have been detained on a European arrest warrant issued by Italian authorities and will appear at a later date before Westminster Magistrates' Court for an extradition hearing.

Rome alleges they are part of a Europe-wide Islamist network of Kurdish-Sunni origins known as Rawti Shax headed by a Norway-based man named Najmuddin Faraj Ahmad, also known as Mullah Krekar.

Another 13 alleged members, including Krekar, were arrested in Italy, Norway, Finland, Germany and Switzerland in an operation coordinated by EU judicial co-operation agency Eurojust, while Italy's Ansa news agency said all 17 alleged extremists are Kurdish or Kosovar.

In October, Ahmad was sentenced to 18 months in jail for praising the Islamist shooting at French satirical newspaper Charlie Hebdo.

Eurojust said Rawti Shax also known as Didi New, which means the "new course" or "towards the mountain" is an offshoot of Ansar Al Islam, a group affiliated with al-Qaeda and listed by the UN as a terrorist organisation.

"Its primary objective is to violently overthrow the current Iraqi Kurdish government and replace it with a caliphate governed by Sharia law," the agency said. "According to the Italian investigation, unlike Ansar Al Islam, Rawti Shax arose and is rooted in Europe, with cells communicating and operating via the internet, with a structure active especially in Germany, Switzerland, the UK, Finland, Italy, Greece, Sweden, Norway, Iraq, Iran and Syria.

"As the group evolved, it became active in providing logistical and financial support to recruiting foreign terrorist fighters [FTFs] to be sent to Syria and Iraq, also with the intent of training them for the future conflict in Kurdistan."

Italian interior minister Angelino Alfano praised the Italian ROS Carabinieri unit that lead the operation saying it was a "wonderful day for the state and the Italian team".