Police arrested three men and a woman accused of leading the group during raids by 250 investigators on homes in Saxony and four other states, the federal prosecutor’s office said.

Prosecutors allege the four helped found the Oldschool Society group and were planning to attack asylum seeker housing, mosques and well-known members of the Islamic-extremist Salafist scene in Germany.

The four arrested, identified only as Andreas H, 56, Markus W, 39, Denise Vanessa G, 22, and Olaf O, 47, in line with German privacy laws, are being held on terrorism charges and are also accused of having procured explosives. The statement identified Andreas H and Markus W as the group’s president and vice president.

“According to current investigations, it was the group’s goal to conduct attacks in smaller groups inside Germany on well-known Salafists, mosques and asylum seeker centres,” the statement said. “For this purpose the four arrested procured explosives for possible terror attacks by the group.”

Prosecutors said they are still trying to determine whether the group had concrete attack plans and refused to comment beyond their written statement.

There have been conflicts in recent years between far-right extremists and Salafists in the western state of North Rhine-Westphalia that have escalated into violent street fights. In 2013, authorities said they foiled a Salafist plot to assassinate a high-ranking member of a far-right party in the state.

German interior minister Thomas de Maiziere said the Oldschool Society appeared to be a newly-formed group.

“We are very glad that it hopefully has been nipped in the bud — everything else will be shown by the investigation,” Mr de Maiziere said.

Rhineland-Palatinate interior minister Roger Lewentz held up what appeared to be the group’s logo — a white skull on black background framed by bloody butcher’s cleavers with lightning bolts resembling the runes of the Nazi SS.

“The SS rune is in there —that’s not for nothing,” Mr Lewentz said.

Right-wing extremists have been a renewed focus for German intelligence agencies after it came to light that a neo-Nazi group calling itself National Socialist Underground, or NSU, allegedly killed eight Turks, a Greek and a policewoman between 2000 and 2007. It is also believed to be behind two bombings and 15 bank robberies.

Mr de Maiziere said statistics just released showed a 22.9% rise in violent crimes by right-wing extremists in 2014 to 1,029 — including 175 attacks on refugee homes, three times the rate in 2013.