German police say one of four Algerian men suspected of plotting an attack in Berlin had registered in Germany as a Syrian refugee and another had contacts in Belgium.

Police, who suspect the four had ties to the Islamic State group, conducted raids Thursday in Berlin and western Germany. One of the Algerians and his wife were arrested at a refugee home because they were sought by Algerian authorities for belonging to the extremist group.

Berlin police said Friday the man arrived in Germany at the end of last year and sought asylum under a Syrian identity. They said they established that another of the Algerians, who wasn't arrested, had contacts with Belgium. They didn't elaborate, but the country has a strong Islamic extremist scene.