The organising committee said Carreira died from injuries sustained in the crash on Thursday afternoon.
"No other rider was involved in the incident, which occurred at Fisherman's Bend ... The qualifying session was immediately red flagged," the committee said in a statement.
"As a result of the doctors' diagnosis, Mr. Carreira was immediately evacuated by ambulance to the hospital."
The 35-year-old from Lisbon died about 30 minutes later, it added.
"The Macau Grand Prix Committee has contacted the family and the members of the team, and the committee expresses its sincere condolences," it said.
"In over 60 years of the Grand Prix, the record can be considered acceptable," coordinator of the Macau Grand Prix committee Joao Manuel Costa Antunes told Hong Kong daily newspaper South China Morning Post.
"Those involved in motorsport and motorbikes know exactly what I'm saying," Antunes said, commenting on the Carreira incident, the second death of a motorbike rider at the track in seven years, and the second serious bike accident of the day.
Organisers did not provide further details to AFP.
Celebrated Italian motorbike rider 24-year-old Marco Simoncelli died last year in a crash that resulted in the cancellation of the Malaysian MotoGP at Sepang.