The tape was installed by a Nazi group sometime before 4am on Tuesday morning, "encouraging" the channel not to report on Holocaust Memorial Day, which is commemorating the date Jews were freed from the Auschwitz-Birkenau concentration camps in Poland.
The letter attached to the tape said:
"The Swedish people don't want to hear people nag about the dead Jews today. This is old and dusty. We should focus and shed light on real tragedies such as the huge amounts of immigrants that are coming to Sweden or the genocide in South Africa. Not with best regards, from the Motståndsrörelsens Kampgrupp in Dalarna."
Motståndsrörelsens Kampgrupp is a sub-group of the neo-Nazi Swedish Resistance Movement.
The Nazi letter blocking the entry to P4 Dalarna. Photo: Johannes Rosendahl
This type of manifestation is a first for the station in Falun, which is the capital of Dalarna County in central Sweden, its assistant editor Johannes Rosendahl told The Local on Tuesday.
"They often let us know how they feel on Twitter, or in their own forums, basically saying that they hate us," he said. "But this message really about our reporting – telling us not to report."
He added that other radio newsrooms in the country have been subjected to similar provocations in the past.
"We report on Nazis in Dalarna fairly often," he said. "But we haven't faced this level of manifestation of hate before."
According to Rosendahl, Dalarna is an increasing stronghold for Nazi activities, and he suspects that "leaders of the movement" may have relocated there.
P4 Dalarna has contacted Sveriges Radio's legal team, which is examining the situation.
Meanwhile, local police visited the radio station on Tuesday morning, collecting the sign and tape surrounding the main entrance.
According to Rosendahl, the provocation will not deter the station's staff from their usual course of work.
"This does not affect our reporting at all. I feel my job is more important than ever."