Germany's domestic intelligence agency put the opposition Alternative for Germany (AfD) party under observation on suspicion of extreme right-wing sympathies, media outlets reported on Wednesday.
The move by the Federal Office for the Protection of the Constitution (BfV) came more than two years after it announced it was examining more closely public comments by party members and links to extremist groups.
In January 2019, the agency put the party's youth arm and another now-dissolved faction, The Wing, under covert surveillance over extremism allegations.
The BfV cited as reasons the youth organisation's goal of creating an ethnically pure country and efforts by The Wing to downplay Germany's Nazi past.
The Wing, linked to Bjoern Hoecke, a leader in eastern Germany, advocated revolutionary means to achieve its political aims.
The BfV refused to comment on the media reports. The Interior Ministry oversees the agency and said it could neither confirm nor deny the reports, but that a statement would be issued on Wednesday.
AfD won 94 seats in the German parliament in 2017 and became the country's third largest party on an anti-immigration and anti-EU platform. But while it was polling at about 15 per cent in 2019, its support has since dropped by about 5 per cent.
Co-chairman Tino Chrupalla accused the BfV of leaking the information to the media in an attempt to influence opinion about the party.
“The behaviour of the BfV is scandalous,” he told news agency dpa International.
