Mario Mandzukic came on as a substitute to head the winner in a 1-0 victory, but Van Buyten credited the home side for their effort in the match.
"It was a difficult game, but we're happy to have won and to have picked up three points," he told UEFA.com. "Playing at home, our opponents were very, very aggressive, so that made it a tough match for us.
"We now have 12 points from four games and we're through to the last 16. We have to look forward as we have some difficult games coming up."
Bayern have qualified with 12 points from their first four games.