A left-wing group called Antifa Halle had sprayed stencil images with the names of the two victims of the October 2019 attack in various locations across the city on Sunday night, according to a report in the Bild daily.
But some of the images with the inscription “Never forget — Kevin and Jana” were smeared with red swastikas on Thursday night, the eve of the anniversary of the Halle attack, the report said.
An investigation has been launched and work has begun to remove the swastikas, police told AFP.
The attack targeting a synagogue in Halle on October 9th, 2019 came during Yom Kippur, the holiest day in the Jewish calendar, and was one of the worst acts of anti-Semitic violence in Germany's post-war history.
A neo-Nazi suspect, 28-year-old Stephan Balliet, is currently on trial for the attack and has told the court it was “not a mistake”.
The suspect had sought to storm the synagogue, but when the door failed to break down, he shot dead a female passer-by and a man at a kebab shop instead, named as Jana L. and Kevin S. by German media.
The Antifa Halle group said in a statement sent to media that its graffiti was intended to draw attention to the fact that nothing has changed a year on from the attack, according to Bild.
Anti-Semitic crimes have risen steadily in Germany in recent years, with 2,032 offences recorded in 2019, up 13 percent on the previous year.
They have sparked soul-searching in Germany, which has placed a huge emphasis on atoning for the murder of six million European Jews by Adolf Hitler's Nazi regime during World War II.
Just this week, a Jewish student was attacked outside a synagogue in Hamburg in a case that police are treating as attempted murder with anti-Semitic intent, condemned by Chancellor Angela Merkel as a “disgrace”.