Nearly 450 police and special commando units conducted pre-dawn raids on Thursday against suspects in the central city of Göttingen after collecting intelligence on plans for a terror attack.

Police chief Uwe Lührig said that indications of a "potentially imminent terror attack" had "solidified to such an extent in recent days," that authorities elected to mobilize against the prime suspects and their close associates.

Two men deemed to pose a threat were taken into custody as part of the operation that targeted a dozen locations. The 27-year-old Algerian national and 23-year-old Nigerian national were long active in the radical Islamist scene in Göttingen and were under surveillance, police said. They were both born in Germany and lived with their parents.

The raids yielded weapons and ammunition as well as "Islamic State" flags, investigators said.

Police displayed at a press conference the weapons, ammunition and IS flags found in the raids.

Boris Pistorius, the state of Lower Saxony's interior minister, called the operation a "very important blow against the [radical Islamist] scene." He said the two men had "very concrete" attack plans, but at the moment it is unclear if the suspects had determined an exact time for an attack.

The raids come as German authorities have conducted a string of operations targeting suspected terror plotters.

The terror threat has prompted the German government to pass a raft of security measures in recent months as security questions and immigration take a prominent role in upcoming national elections in September.

cw/msh (AFP, dpa)