SHANGHAI - New Orleans mayor Ray Nagin has left China after being quarantined in Shanghai following a swine flu scare, his spokesman said on Thursday.

Nagin, who was held Sunday after a fellow passenger on his flight fell ill with a suspected case of the influenza A(H1N1) virus, left China late Wednesday, his spokesman James Ross told AFP.

Nagin had already arrived in Sydney, the next stop on his trip, said Ross, speaking from the Australian city.

He said the enforced quarantine caused Nagin to miss several meetings in the Chinese business hub.

"He was certainly disappointed that he was not able to go to the meetings as he had planned," Ross said.

"But the mayor has said that he understands the decision of the Chinese government and that he was treated with the utmost courtesy."

The delay would not affect his schedule in Australia, Ross added.

Nagin, who is on a trip to stir up business for his city, was originally scheduled to leave Shanghai on Tuesday night.

He is scheduled to appear with the mayor of Sydney on Thursday and give a speech on climate change at the University of Sydney on Friday.

China's strict flu control measures have faced foreign criticism.

Authorities have submitted passengers to temperature checks and at times quarantine at its airports in a bid to stop the spread of swine flu.

Those placed under quarantine have usually been released after a seven-day observation period.

On Tuesday, Chinese health authorities announced that there were more than 100 confirmed cases of the virus on the mainland.

China confirmed its first case of the illness - which has killed 141 people in six countries - on May 11, but it has so far recorded no deaths.

Nagin shot to national prominence in the United States in 2005 with his harsh criticisms of the slow federal response to Hurricane Katrina, which devastated the city.