Flares were thrown on the pitch during the West Ham's game at Genk.
Uefa has banned West Ham fans from travelling to the game in Rapid Vienna.
In a statement, West Ham said they were reluctantly accepted the sanctions, but also wanted to make clear their disappointment at the short notice of the measures.
The game is against Rapid Vienna.
The club said that they were working to identify the fans who caused the trouble.
The group of individuals were condemned by West Ham United.
The majority of our supporters behaved well in Belgium, which resulted in them being punished and the team being forced to play in Austria without the support of the club's fans.
The Hammers urged their fans not to travel to Vienna for the tie.
Fans will not be allowed to enter the stadium and any attempt to enter could lead to further sanctions for the individuals and the club in the future.
Group H has 10 points after four games.
