The monument, which shows a hammer crushing a swastika, was designed by artist Bjørn Melby Gulliksen and unveiled on May 1st 2015.
The statue commemorates the actions of the Osvald Group and employees of Norway's state railway NSB who took part in sabotage missions as part of Norway's resistance against the German occupation during the Second World War.
The Osvald Group was Norway's most active resistance movement during World War Two, and carried out hundreds of sabotage missions against German infrastructure, war industry and troops.
Thursday marks the 75-year anniversary of what is considered to be the date marking the beginning of the Holocaust in Norway.
On October 25th 1942, Norwegian Jews over the age of 15 were interned, possessions were seized and Jewish women required to report to authorities.
It is unknown whether there is any connection between the act of vandalism and the anniversary, reports newspaper VG.