BERLIN

German police have arrested a 17-year-old right-wing extremist and his 59-year-old father after discovering a large cache of weapons and explosives at their home, public broadcaster ARD reported on Friday.

Frankfurt prosecutors said they are investigating the two for violations of weapons control and explosives laws, as well as incitement to hatred and making threats. The suspects remain in custody due to flight risk.

The arrests took place in the Limburg-Weilburg district in western Hesse.

According to investigators, the father stored a large cache of weapons, including machine guns, in his house along with at least 250 kilograms of ammunition. They were discovered and seized during searches at the house.

The 17-year-old was suspected of acquiring a firearm and ammunition recently and manufacturing explosives, which he later tested in a forest. He had previously drawn authorities' attention through extremist statements online and was accused of using symbols of a former Nazi organization.

Prosecutors said the teenager was suspected of “planning a serious act of violence,” without providing further details. Prosecutors also reported that searches were conducted at the homes of two other teenagers who were suspected of assisting him.

Right-wing terror and violence remain Germany's most pressing security concern, according to the Interior Ministry. In recent years, small, previously unknown neo-Nazi groups and lone actors have carried out numerous attacks targeting politicians, migrants, synagogues, and mosques. According to official figures, right-wing extremist crimes rose to 41,406 last year, including 1,443 violent attacks against migrants, refugees, and political opponents. At least 521 people were injured in these attacks.