BERLIN — Four teenagers suspected of planning an Islamic extremist attack have been arrested in Germany, authorities said on Friday.

Three of the suspects — two girls who are 15 and 16, and a 15-year-old boy — come from various parts of the western North Rhine-Westphalia state, Germany's most populous. They were arrested after a court issued warrants for them over the Easter weekend, prosecutors in the city of Duesseldorf said.

A fourth suspect, a 16-year-old boy, was arrested in the southwestern state of Baden-Wuerttemberg, German news agency dpa reported.

The three detained in western Germany are suspected of having declared themselves prepared to carry out an “Islamist-motivated terror attack” and planning such an attack, prosecutors said in a statement. They didn't specify how advanced the plans were, and said they couldn't give further details because of the suspects' young age and the ongoing investigation.

They are in detention pending possible charges of declaring themselves ready to commit murder and manslaughter and preparing a serious act of violence.

North Rhine-Westphalia's top security official, state Interior Minister Herbert Reul, said the investigation was prompted by the 16-year-old girl's suspected plans to leave Germany to join the Islamic State group.

Chats on her cellphone, in which possible attacks in Dortmund, Duesseldorf or Cologne were discussed but also churches and synagogues in her home town of Iserlohn, led investigators to the other suspects, dpa reported.

Citing unidentified security sources, the agency reported that the teenagers hadn’t yet drawn up a concrete attack plan with a time and place.