Image caption Tumbledown Trails Golf Course said the discount was to commemorate the 12th anniversary of the 9/11 attacks

The owner of a Wisconsin golf course that advertised nine holes of golf for $9.11 to mark the 12th anniversary of the 9/11 attacks has apologised after a backlash that included death threats.

The company's Facebook page was overrun with negative comments after the discount appeared in a paper on Monday.

Owner Marc Watts said he would keep the course open despite receiving threats to burn down the premises.

The discount was reportedly not new and had been running for three years.

An advert for the discount offered by Tumbledown Trails Golf Course featured in the Wisconsin State Journal earlier this week, saying it was intended to commemorate the 12th anniversary of the 2001 attacks in New York that killed nearly 3,000 people.

It said the discount, which also included 18 holes of golf for $19.11, was valid for the anniversary on 11 September only.

Responding to negative comment on the discount, owner Marc Watts apologised on the golf course's Facebook page saying there was no intention to cause offence and pledged to donate some of the day's earnings to the 9/11 memorial in New York.

"We're a little hurt by the fact that people are putting such a negative context on this," Mr Watts said in an interview with the Associated Press news agency. "I thought people would appreciate it."

He added: "We could close, but then all these people with their negative attitudes, they win.''