The attacks started at the end of last week, when one of Djurgården’s training grounds was found to have been dug up. On Sunday night somebody released a smoke bomb in the cellar of an apartment block in which two AIK players live.
“The smoke bomb could be a response from a supporter to the dug-up pitch,” said Marie-Louise Nilsson of Stockholm Police.
Lewd graffiti has also been found in the stairwell of an apartment block in which AIK stars Lucas Valdemarin and Ivan Obolo live.
Police say they believe the incidents are psychological warfare between rival supporters.
“We have received reports,” said Nilsson.
“It’s really mostly up to the clubs to investigate.”
Police are now concerned at what supporters might get up to in the run up to Monday evening’s match.
“These incidents will hardly affect the footballers, but they could enrage the fans”, Nilsson said.
Police are treating the smoke bomb and the graffiti as acts of vandalism, although they say it is possible that the smoke bomb was not targetted at the footballers.