Standard were leading 2-0 in Liege when the referee abandoned the match after 32 minutes. The players had already been forced from the field twice before.
"The match has been definitely stopped because of the behaviour of the RSC Anderlecht supporters," Standard said in a tweet.
The Belgian first division said it regretted the premature ending of the match and said that it would lead to sanctions as well as an investigation by federal prosecutors.
Under Belgian rules, sanctions can include forfeiting a match 5-0, a fine and the possibility of having to play matches without supporters present.
Anderlecht had lost all three previous matches in the playoffs to date and their fans expressed their disappointment last weekend after a 2-1 loss at home to Antwerp, calling for the chairman to go. Some supporters also clashed with police.
The Brussels-based club said on Twitter that they regretted what had happened on Friday.
"The board of RSC Anderlecht strongly condemns the behaviour this evening. This is absolutely intolerable for football," the club said.
(Reporting by Philip Blenkinsop; Editing by Toby Davis)
