Oxford United have apologised for launching a clothing collection branded 'United 93' a week after the 25th anniversary of the Sept. 11 terrorist attacks.

Nearly 3,000 people were killed in 2001 when hijacked passenger jets struck the World Trade Center in New York and the Pentagon outside Washington. A fourth plane, United Airlines Flight 93, crashed into a field in rural Pennsylvania after passengers fought back.

The Oxford United Campus Collection reportedly included an American football jersey and a baseball jersey featuring the term 'United 93'. The club stated the range was released "without understanding of the historical context and associations" and admitted it should not have reached the point of sale.

"We take full responsibility for not undertaking proper due diligence," the League One club said. "We have removed the collection with immediate effect and are reviewing our approval processes to ensure nothing like this happens again."

Oxford United were founded in 1893 and celebrated promotion to the old Second Division in 1993.