BERLIN (AP) — German authorities arrested four Syrian brothers on terrorism charges Monday for allegedly fighting for an extremist group in their homeland five years ago.

Mustafa K., 41, Abdullah K., 39, Sultan K., 44, and Ahmed K., 51, whose last name wasn't released because of privacy regulations, are accused of membership in a terrorist organization for fighting for the Nusra Front in the northern Syrian city Ras al-Ayn starting in late 2012.

Federal prosecutors said the men were allegedly involved in the group's fight against Syrian government troops and Kurdish defense forces.

Mustafa and Sultan K. are also charged with war crimes for allegedly forcing civilians from the city and plundering their possessions. Prosecutors refused to say when the brothers entered Germany.

In a separate case, prosecutors said Monday that a 31-year-old Syrian arrested in February has been released. He was accused of membership in the Islamic State group and of committing a war crime by raping a woman as she tried to flee IS-controlled territory in Syria.

The suspect, Akram A, was released on Friday, federal prosecutors said in a statement.

Prosecutors have said that the suspect ran an IS checkpoint set up to control people leaving territory held by the group. The allegations relate to an incident in early 2016 in which a Syrian woman tried to flee with her children.

Prosecutors said Monday further investigations now suggest that "a different sequence of events" is also possible, but didn't offer details. That meant that the evidence was no longer strong enough to justify keeping him in custody.