Opoku, who was born in Hamburg but is of Ghanaian descent, was subjected to monkey chants by fans of the home team.
The treatment meted out to the Osnabrück forward led to referee Nicolas Winter stopping the game in the 35th minute.
Ten minutes after the incident, the referee decided to call off the match after Osnabrück decided not to continue.
“There was a corner for Osnabrück, and when the player wanted to take it, there were monkey sounds from the stands. He noticed it immediately and so did the assistant. Both of them described it to me," the referee said, as quoted by Sports Star.
The report added that Opoku was shocked by the racial chants aimed at him and was visibly distraught.
Meanwhile, Duisburg press officer Martin Haltermann condemned the incident, insisting the club doesn’t support such acts.
“Osnabrück – and that is more than understandable – can no longer compete. The guy is in bits and everyone — the whole team — is distraught,” he said.
“Honestly, we are too after this incredible incident. We’re all pretty speechless at the moment.”
Osnabrück’s managing director Michael Welling added: “Aaron is very, very deflated and no longer able to play. That’s one of the reasons we said we would not play on,” said Welling, who added that racism had “no place in society and therefore also not in soccer.”
In recent years, some Ghanaian footballers have made the news after being racially abused, including Sulley Muntari and Kevin-Prince Boateng.