Copenhagen (Alshahid)-Danish police have detained two brothers from Somalia on suspicion of plotting an attack, the state security police said on Tuesday.

The Danish Security and Intelligence Service (PET) said early on Tuesday that two brothers aged 18 and 23 were arrested the previous evening on suspicion of planning “a terrorist act.”

One was arrested in the city of Aarhus, the other was apprehended at Copenhagen airport as he returned to the country.

The police described both men as Danish citizens of Somali origin, and said they had lived in the central city of Aarhus – some 170 kilometers (105 miles) west of Copenhagen – for the past 16 years.

“One of the detainees is also suspected of having voluntarily been trained, instructed or taught at an Alshabab training camp in Somalia with a view to committing acts of terrorism,” the PET said.

The arrests come as four other men stand trial in Denmark for allegedly plotting a 2010 attack on the offices of a Danish newspaper that published cartoons of the Prophet Mohammed in 2005. A verdict in that case is expected next month.