BERLIN (AP) — German authorities have detained a Syrian man on suspicion of planning to carry out an explosives attack motivated by Islamic extremism, officials said Tuesday.

Federal police said officers detained the 28-year-old man early Tuesday in the northern city of Hamburg.

Investigators say the man is suspected of trying to obtain substances online that would have allowed him to manufacturer an explosive belt “in order to carry out an attack against civilian targets.”

Police say the man was encouraged and supported in his action by his 24-year-old brother, who lives in the southern town of Kempten. The men, whose names weren't immediately released, are described as being motivated by “radical Islamist and jihadist” views.

Authorities said they had no information indicating a concrete target for the planned attack.

Police searched properties in Hamburg and Kempten, seizing large amounts of evidence including chemical substances, officials said. Some 250 officers were involved in the operation.