People in Austria were doing double takes when they saw a man resembling Hitler walking down their street.

The man, in his twenties, has been seen at Hitler's birthplace Braunau am Inn and was allegedly spotted reading World War II magazines at a local bookshop. He apparently dons the same clothing as the Nazi dictator and imitates his short moustache and haircut.

Police are investigating after reports the man walked into a bar and identified himself as Harald Hitler, according to a report in Sky News.

He was also pictured outside the house where Hitler was born in 1889 in Austria-Hungary.

One resident posted a picture of the man on Facebook, saying: "I have often seen this gentleman in Braunau and wonder if this means something."

The parliament in Austria voted last year to buy the three-storey house where Hitler grew up, which the government has leased since 1972. Government officials plan to redesign the property's facade and offer it to Lebenshilfe, a charity which supports people with learning difficulties.

Glorifying Hitler or the Nazis is a criminal offence in Austria, which was annexed by Nazi Germany in 1938 for the Third Reich.

Austrian Chancellor Kurt von Schuschnigg pleaded with Hitler to keep the country's independence amid a conspiracy by Austrian Nazis to take the Austrian government by force. Schuschnigg later gave in to pressure from Hitler and resigned on March 11.

He was imprisoned by the Nazis, who then took control of the country, appointed a new Nazi government and proclaimed Anschluss — the formal annexation of Austria into Germany. Schuschnigg was later released in 1945 after the allied powers declared the annexation void and re-established an independent Austria.

There has been concern over a resurgence of right-wing politics in Austria. Norbert Hofer of the far-right Freedom Party of Austria made the run-off for the presidency last year, losing out to Alexander van der Bellen.